HEATING  AND  VENTILATION 


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.HEATING 

AND 

VENTILATION 


BY 

THE  LATE 

JOHN  ft.  ALLEN   Gre. 


DIRECTOR  OP  RESEARCH  LABORATORY  OP  AMERICAN  SOCIETY  OF  HEATING  AND  VENTILATING 
ENGINEERS;  FORMERLY  DEAN  OF  ENGINEERING  AND  ARCHITECTURE,  UNIVERSITY  OP 
MINNESOTA;  PAST  PRESIDENT  AMERICAN  SOCIETY  OP  HEATING  AND  VENTI- 
LATING ENGINEERS;  MEMBER  AMERICAN  SOCIETY  OP  MECHANICAL 
ENGINEERS 

AND 


J.  H.  WALKER 


SUPERINTENDENT   OF  CENTRAL  HEATING,    THE  DETROIT  EDISON  COMPANY;  MEMBER  AMERICAN 
SOCIETY   OF  HEATING   AND  VENTILATING   ENGINEERS;    PRESIDENT 
NATIONAL  DISTRICT  HEATING   ASSOCIATION    1922 


SECOND  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 
NEW  YORK:  370  SEVENTH  AVENUE 

LONDON:  6  &  8  BOUVERIE  ST.,  E.  C,  4 
1922 


COPYRIGHT,  1918,  1922,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY,  INC. 


THE    MAPLE    FKESS    T  O  H  K 


PREFACE  TO  SECOND  EDITION 

A  second  edition  of  this  book  has  become  desirable  because  of 
the  advances  in  the  art  which  have  been  made  during  the  last 
few  years,  such  as  the  establishment  of  ventilation  standards 
and  the  work  of  the  Research  Laboratory  of  the  American  Society 
of  Heating  and  Ventilating  Engineers.  Much  of  the  new  material 
is  taken  directly  from  Professor  Allen's  writings  while  Director 
of  the  Laboratory  during  the  last  year  of  his  life. 

Several  of  the  chapters  have  been  entirely  rewritten  and  a  more 
logical  arrangement  has  been  adopted.  The  entire  book  has 
been  thoroughly  revised  and  slightly  enlarged.  The  aim  has 
been  to  increase  in  every  possible  way  its  value  as  a  college  text 
book,  in  which  field  it  has  come  to  be  widely  used. 

Acknowledgment  is  made  to  Prof.  H.  C.  Anderson  of  the 
University  of  Michigan  for  his  valuable  advice  and  criticism  and 
to  the  many  others  who  have  contributed  various  material, 
credit  for  which  is  given  throughout  the  book. 

September,  1921.  J.  H.  W. 


PREFACE  TO  FIRST  EDITION 

This  book  is  offered  as  a  text-book  upon  the  subject  of  heating 
and  ventilation  for  use  in  the  engineering  and  architectural 
schools.  It  is  also  believed  that  the  development  of  working 
methods  of  design  and  the  including  of  the  various  tables  and 
charts  make  the  book  of  some  value  as  a  handbook  for  the 
practicing  engineer  and  architect. 

Calculus  has  been  employed  to  some  extent  in  the  develop- 
ment of  certain  expressions,  this  having  been  deemed  desirable 
for  the  sake  of  completeness.  For  architectural  students  and 
others  not  equipped  with  higher  mathematics,  such  parts  may 
be  omitted,  however,  without  destroying  the  structure  of  the 
book.  Problems  have  been  included  at  the  end  of  many  of  the 
chapters  in  order  to  illustrate  the  principles  involved,  but  it  is 
felt  that  they  can  be  profitably  supplemented  by  the  actual 
designing  by  the  student  of  complete  heating  and  ventilating 
systems  for  representative  buildings  of  various  types. 

Acknowledgment  is  made  to  the  American  Blower  Company 
and  the  Buffalo  Forge  Company  for  the  use  of  various  charts 
and  tables. 

Information  as  to  the  typographical  errors  which  are  doubtless 
present  in  this  initial  edition  will  be  gratefully  received. 

J.  R.  A. 

March,  1918.  J.  H.  W. 


CONTENTS 

PAGE 

PREFACE  TO  SECOND  EDITION  ...................  v 

PREFACE  TO  FIRST  EDITION   ...................  vii 

CHAPTER  I 

HEAT* 

Measurement  of  Heat  ......................  1 

Measurement  of  Temperature   ..................  2 

Unit  of  Heat  ..........................  4 

CHAPTER  II  V 

HEAT  LOSSES  FROM  BUILDINGS 

Radiation   ...........................  9 

Conduction   ..........................  10 

Convection   ..........................  11 

Loss  of  Heat  from  Buildings  ...................  12 

Heat  Lost  Due  to  Infiltration  ...................  19 

Calculation  of  Heat  Loss  .....................  21 

CHAPTER  III 

DIFFERENT  METHODS  OF  HEATING 

Grates  .............................  25 

Stoves  .............................  26 

Hot-air  Furnaces  ........................  27 

Direct  Steam  Heating  ......................  28 

Direct  Heating  by  Hot  Water    ..................  28 

Indirect  Heating   ........................  30 

Economy  of  Heating  Systems   ..................  32 


CHAPTER  IV 

HOT-AIR  FURNACE  HEATING  / 

Furnaces  ............................  35 

Cold-air  Pipe  ..........................  39 

Hot-air  Pipes  .    .........................  40 

Pipeless  Furnaces  ........................  46 

ix 


x  CONTENTS 

CHAPTER  V 

PROPERTIES  OF  STEAM 

PAGE 

The  Formation  of  Steam. 49 

Properties  of  Steam 50 

Steam  Tables 52 

Mechanical  Mixtures 54 

CHAPTER  VI 

RADIATORS 

Direct  Cast-iron  Radiators 61 

Pressed  Metal  Radiators 65 

Heat  Transmission  from  Radiators 67 

Location  of  Radiators 78 

Proportioning  Radiation 81 

Indirect  Radiators 83 

CHAPTER  VII  / 

STEAM  BOILERS  •< 

Fuel 92 

Combustion 95 

Smoke 95 

Types  of  Boilers 98 

The  Downdraft  Boiler .    .  V 101 

Boiler  Rating - .    .    . 105 

Draft  and  Chimney  Construction 110 

CHAPTER  VIII 

STEAM  HEATING  SYSTEMS  v 

Single-pipe  Systems 113 

Two-pipe  Systems •  . 115 

Overhead  System 117 

Vapor  System 119 

Vacuum  Return  Line  System .    .    .  •... .« 125 

CHAPTER  IX 

PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES 

Pipe 127 

Fittings 129 

Valves 132 

Pipe  Covering 134 

Air-valves 137 

Traps 138 

Reducing  Valves 141 


CONTENTS  xi 
CHAPTER  X 
STEAM  PIPING 

PAGE 

Principles  Involved  in  Piping  Design 145 

Expansion 145 

Drainage 146 

Mains  and  Branches 147 

Risers 149 

Pipe  Hangers 150 

Radiator  Connections 154 

Flow  of  Steam  in  Pipes 157 

Selection  of  Pipe  Sizes 160 

CHAPTER  XI 

HOT-WATER  SYSTEMS 

Theory  of  Flow  in  a  Gravity  System 168 

Types  of  Gravity  Systems 172 

Method  of  Computing  Pipe  Sizes :  177 

Forced  Circulation 184 

Pumpage,  Friction,  and  Temperature  Drop 185 

Calculation  of  Pipe  Sizes 185 

CHAPTER  XII 

TEMPERATURE  CONTROL 

Manual  Control 189 

Automatic  Control  Applied  to  Boiler 190 

Automatic  Control  of  Radiators 192 

Advantages  of  Automatic  Control 194 

CHAPTER  XIII 

AIR  AND  ITS  PROPERTIES 

Composition  of  Air 196 

Water  Vapor 197 

Measurement  of  Humidity 200 , 

Psychrometric  Chart 202 

CHAPTER  XIV 

VENTILATION 

Ventilation  Standards 206 

Amount  of  Air  Required 209 

Methods  of  Measuring  Air  Supply 209 

Temperature  and  Humidity 211 

Air  Movement  .                                                                                              .  213 


xii  CONTENTS 

PAGE 

Odors 214 

Dust  and  Bacteria 215 

Ventilation  Tests 215 

Synthetic  Air  Chart. .y<   ......  216 

CHAPTER  XV 

FAN  SYSTEMS  FOR  VARIOUS  TYPES  OF  BUILDINGS 

Office  Building  Systems 226 

School  Building  Systems. 226 

Factory  Heating 231 

Unit  Ventilators 234 

CHAPTER  XVI 

DESIGN  OF  FAN  SYSTEMS 

Calculation  of  Air  Quantities 237 

Flow  of  Air  in  Ducts  . 239 

Proportioning  Duct  Systems 247 

Theory  of  the  Centrifugal  Fan 253 

Fan  Performance 256 

Selection  of  a  Fan 258 

Heaters 263 

Transmission  of  Heat  from  Fan  Coils 266 

CHAPTER  XVII 

AIR-WASHERS  AND  AIR  CONDITIONING 

The  Air-washer 274 

Air  Conditioning 276 

Humidity  Control 278 

Cooling  and  De-humidification 281 

CHAPTER  XVIII 

CENTRAL  HEATING 

Location  of  Power  Plant 283 

Systems  of  Distribution 285 

Methods  of  Carrying  Pipes 287 

Expansion  Fittings 289 

Tunnels 291 

Commercial  District  Heating 293 

INDEX.                                                                                                           .  327 


HEATING  AND   VENTILATION 

CHAPTER  I 
HEAT 

1.  Heat. — Heat  has  long  been  known  to  be  a  form  of  energy. 
Modern  theories  as  to  the  exact  nature  of  heat  conceive  it  to  be  a 
motion  or  agitation  of  the  molecules,  or  extremely  small  particles, 
of  which  every  substance  is  composed.     The  intensity  of  the 
heat  in  a  body  is  believed  to  be  dependent  upon  the  violence 
of  this  molecular  disturbance.     Every  substance  on  the  earth 
contains  some  heat  and  to  say  that  a  body  is  "cold,"  means 
simply  that  it  contains  a  relatively  small  amount  of  molecular 
motion. 

Heat  and  many  other  forms  of  energy  are  mutually  convertible. 
For  example,  heat  energy  is  converted  into  electrical  energy  in  a 
generating  plant  and  electric  energy  is  re-converted  into  heat 
energy  in  an  electric  stove.  Heat  energy  is  converted  into 
mechanical  energy  in  a  steam  locomotive  and  some  of  this 
mechanical  energy  is  re-converted  into  heat  energy  by  the 
friction  of  the  locomotive  brakes. 

2.  Measurement  of  Heat. — In  measuring  heat  there  are  two 
quantities  to  be  considered :  the  intensity  of  heat  and  the  amount 
of  heat.     A  small  piece  of  white-hot  metal  may  not  contain  as 
great  a  quantity  of  heat  as  a  pail  of  warm  water,  but  the  intensity 
of  the  heat  in  the  former  is  much  greater.     The  intensity  -m* 
heat  is  denoted  by  the   word  temperature.     The  temperature  Ir^ 
of  a  body  is  most  easily  measured  by  noting  its  effect  upon  some 
other  substance. 

One  measure  of  the  iiitensity  of  heat  in  a  body  is  its  ability  to 
transmit  heat  to  a  body  of  loweTTelnpefature.  Heat  will  flow 
from  a  body  "of  higher  temperature  to  one  of  lower  temperature 
but  will  never  flow,  of  itself,  from  one  body  into  another  of  higher 
temperature.  When  two  bodies  of  different  temperatures  are 
placed  in  contact  a  heat  exchange  takes  place  until  the  two 
bodies  are  at  the  same  temperature  and  thermal  equilibrium  is 
reached.  We  may,  therefore,  state  that  two  bodies  are  at  the 


"H&ATING  AND  VENTILATION 

same  temperature  when  there  is  no  tendency  for  heat  to  flow  from 
the  one  to  the  other. 

3.  Measurement  of  Temperature.  —  The  measurement  of  tem- 
perature is  usually  based  upon  some  arbitrary  scale  which  is 
standardized  by  comparison  with  some  well-established  ^phys- 
ical, fixed  points.  In  mechanical  engineering  most  measure- 
ments of  temperature  are  made  on  the  Fahrenheit  scale.  On 
this  scale  the  freezing  point  of  water  is  taken  at  32°  and  the 
boiling  point  at  sea  level  barometer  at  212,°  the  tube  of  the 
thermometer  between  these  points  being  divided  into  180  equal 
parts  or  degrees.  There  is,  however,  an  increasing  use  of  the 
Centigrade  scale  among  engineers.  In  the  Centigrade  scale 
the  distance  between  the  freezing  point  and  the  boiling  point  is 
divided  into  100  equal  parts.  The  freezing  point  on  the  scale 
is  marked  0  and  the  boiling  point  is  marked  100°. 

If  the  temperature  Fahrenheit  is  denoted  by  tj  and  the  tempera- 
ture Centigrade  by  tc,  then  the  conversion  from  one  scale  to  the 
other  may  be  made  by  the  following  equations: 


tc  =  ~  (tf  -  32) 

The  most  common  instrument  for  measuring  temperature  is 
the  mercury  thermometer.  Mercury  like  most  other  substances 
undergoes  an  increase  in  volume  when  heated,  and  is  particularly 
useful  because  the  amount  of  its  expansion  for  equal  increments 
in  temperature  is  nearly  constant  over  a  wide  range  in  tempera- 
ture. The  thermometer  is  a  glass  tube  of  very  fine  bore  with  a 
bulb  blown  on  one  end  and  filled  with  mercury,  as  shown  in 
Fig.  1.  The  air  is  expelled  from  the  tube  by  boiling  the  mercury 
and  the  tube  is  sealed.  The  space  above  the  mercury  then  con- 
tains mercury  vapor  at  a  very  low  pressure.  The  329  and  the 
212°  points  of  the  Fahrenheit  scale  are  located  on  the  stem  by 
immersing  the  bulb  in  a  freezing  mixture  and  in  boiling  water.  The 
distance  between  these  points  is  then  divided  into  180  equal  parts. 

To  do  accurate  work  with  the  thermometer  is  much  more 
difficult  than  is  generally  supposed.  The  mercury  of  the  ordi- 
nary glass  thermometer  does  not  expand  in  exactly  equal  amounts 
for  equal  increments  of  temperature  and  the  bore  of  the  ther- 
mometer is  never  absolutely  uniform  throughout  the  length  of  the 
tube.  All  of  these  irregularities  produce  errors.  When  measur- 


HEAT  3 

ing  the  temperature  of  liquids  the  depth  to  which  the  thermom- 
eter is  immersed  affects  the  reading  and  the  thermometer 
should  be  calibrated  at  the  depth  at  which  it  is  to  be  used. 

It  is  really  its  own  temperature  that  the  thermometer  ^ 
indicates  and  the  accuracy  with  which  the  temperature 
of  a  substance  is  measured  depends  upon  the  complete- 
ness with  which  its  temperature  is  reached  by  the 
thermometer.  The  thermometer  must  therefore  be 
brought  into  intimate  contact  with  the  substance  to  be 
measured.  In  measuring  the  temperature  of  fluids  in 
pipes,  a  brass  or  steel  well  is  inserted  into  the  pipe  and 
filled  with  some  liquid  such  as  oil  or  mercury,  in  which  the 
thermometer  is  immersed.  If  the  thermometer  is  used 
to  measure  the  temperature  of  the  air  in  the  room  in 
which  there  are  objects  of  a  higher  temperature  than 
the  thermometer,  its  bulb  must  be  protected  from  the 
radiant  heat  of  these  hot  bodies;  otherwise  the  ther- 
mometer will  not  read  the  temperature  of  the  air  sur- 
rounding it  but  will  be  affected  by  the  radiant  heat 
absorbed  by  it.  When  accurate  temperature  measure- 
ments are  desired  a  careful  study  should  be  made  of  the 
thermometer  and  its  errors  and  all  inaccuracies  should 
be  allowed  for  by  careful  calibration. 

The  mercury  thermometer  can  be  used  up  to  tem- 
peratures of  500°F.  and  for  temperatures  as  low  as 
—  40°.  Where  lower  temperatures  must  be  measured 
it  is  customary  to  use  thermometers  filled  with  alcohol, 
and  for  temperatures  higher  than  500°F.  some  form  of 
pyrometer  must  be  used. 

The  most  common  form  of  pyrometer  is  the  thermo- 
couple, whose  operation  depends  on  the  fact  that  when 
two  different  metals  are  brought  into  contact  and  the 
point  of  junctipn  heated  above  the  remainder  of  their 
length,  an  electromotive  force  is  produced.  If  the  un- 
heated  ends  of  the  two  elements  are  connected  by  a  Fl0'  1> 
metallic  conductor  this  electromotive  force  will  produce  a  flow  of 
current  through  the  circuit.  The  electromotive  force  will  vary 
according  to  the  temperature  of  the  junction  and  is  measured  by 
means  of  a  sensitive  galvanometer  which  may  be  calibrated  to 
read  directly  in1}  degrees  of  temperature.  Thermocouples  may 
be  made  of  a  pair  of  rare  metals  such  as  platinum  and  a  platinum- 


HEATING  AND  VENTILATION 


rhodium  alloy,  or  of  base  metals,  such  as  a  nickelsteel  alloy  and 
copper. 

High  temperatures  may  be  determined  approximately  by 
color.  For  each  temperature  there  is  a  corresponding  color  and 
an  approximation  to  the  actual  temperature  can  be  made  by 
an  observation  of  the  color  of  the  heated  substance.  Table  I 
gives  the  temperature  colors. 

TABLE  I. — TEMPERATURE  COLORS 


Color 

Temp.  C. 

Temp.  F. 

Faint  red  

525 

977 

Dark  red  

700 

1  292 

Faint  cherry  

800 

1  472 

Cherry.  .  .  . 

900 

1  652 

Bright  cherry  

1  000 

1  832 

Dark  orange     .          ... 

1  100 

2012 

Bright  orange 

1  200 

2  192 

White  heat  

1,300 

2372 

Bright  white 

1  400 

2552 

Dazzling  white  

1,500-1,600 

2,732-2,912 

4.  Absolute  Temperature. — In  any  theoretical  consideration 
of  heat  it  is  necessary  to  have  some  absolute  scale  of  temperature. 
The  point  at  which  the  molecules  of  a  substance  would  have  no 
motion  is  considered  to  be  the  absolute  zero  point.     According 
to  Marks  and  Davis  this  point  is  theoretically  at  491.64°  below 
the  freezing  point  of  water  on  the  Fahrenheit  scale,  or  459.64° 
below  the  Fahrenheit  zero.     On  the  Centigrade  scale  the  absolute 
zero  is  at  —273.1°.     To  convert  any  temperature  on  the  Fahren- 
heit or  Centigrade  scale  to  absolute  temperature  the  following 
formulae  are  used: 

Tf  =  tf  +  459.6 

Tc  =  tc  +  273.1 

in  which  the  absolute  temperatures  on  the  Fahrenheit  and  Cen- 
tigrade scales  are  represented  by  Tf  and  Tc. 

No  one  has  as  yet  been  able  to  produce  a  temperature  as  low 
as  the  absolute  zero.  The  lowest  temperatures  ever  attained 
have  been  produced  in  the  heat  laboratory  at  Leyden,  Holland, 
at  which  there  has  been  produced  a  temperature  of  4§9°  below 
the  Fahrenheit  freezing  point.  ?*  * 

5.  Unit   of   Heat. — Heat   must   be   measured   by  the   effect 
which  it  produces  upon  some  substance.     The  unit  of  heat  used 


HEAT  5 

in  mechanical  engineering  is  the  heat  required  to  raise  the  tem- 
perature of  a  pound  of  water  one  degree  Fahrenheit.  This  is 
called  the  British  thermal  unit  and  is  denoted  by  B.t.u.  As  this 
quantity  is  not  exactly  the  same  at  all  temperatures  it  is  necessary 
to  specify  further  a  definite  temperature  at  which  the  unit  is  to 
be  established.  The  practice  of  different  authorities  varies  in 
this  regard,  but  the  mean  B.t.u.  established  by  Marks  and 
Davis  is  becoming  generally  used.  This  is  defined  as  the  one 
hundred  and  eightieth  part  of  the  heat  necessary  to  raise  the 
temperature  of  one  pound  of  water  from  32°  to  212°F. 

6.  Specific  Heat.  —  Specific  heat  may  be  defined  as  the  heat 
necessary  to  raise  the  temperature  of  a  unit  weight  of  a  sub- 
stance through  one  degree.  It  represents  the  specific  thermal 
capacity  of  a  body.  In  English  units  the  specific  heat  is  the 
quantity  of  heat  necessary  to  raise  a  pound  of  a  substance  one 
degree  Fahrenheit,  expressed  in  British  thermal  units.  Since 
the  British  thermal  unit  is  the  quantity  of  heat  necessary  to 
raise  aTpounbro^water  one  degree  Fahrenheit,  we  may  say  that 
the  specific  heat  represents  thejratio  between  the  heat  necessary 
to  raise  a  unit  weight  of  a  body  one  degree  and  the  heat  neces- 
sary to  raise  the  same  weight  of  water  one  degree. 

When  a  substance  is  heated  at  constant  pressure  its  volume 
increases  against  that  pressure  and  external  work  is  done  as  a 
consequence.  The  exterrjal  work  may  be  computed  by  multiply- 
ing the  pressure  by  the  change  in  volume.  When  heated  at 
constant  volume  no  external  work  is.  done  as  no  movement  is 
made  against  an  external  resistance.  In  any  substance,  such  as 
a  gas,  which  has  a  large  coefficient  of  thermal  expansion,  the 
specific  heat  of  constant  volume  will  have  a  different  value  from 
the  specific  heat  of  constant  pressure,  the  latter  being  the 
greater.  The  difference  between  the  two  specific  heats  in  any 
particular  gas  must  be  equal  to  the  heat  equivalent  of  the  exter- 
nal work  done  when  a  unit  weight  of  the  .gas  is  raised  one  degree 
at  a  constant  pressure.-- 

The  quantity  of  heat  added  to  or  removed  from  a  body  is 
equal  to 


in  which 

W  =  weight  of  the  body*  in  pounds. 
C    =  specific  heat  of  the  material. 
ti    =  lower  temperature  Fahrenheit. 
t»    =  higher  temperature  Fahrenheit. 


HEATING  AND  VENTILATION 
TABLE  II. — SPECIFIC  HEATS 

Substance  Specific 

heat 

Liguidt: 

Water 1.0000 

Alcohol 0.6220 

Turpentine 0.4720 

Petroleum 0.4340 

Olive  oil 0 . 3090 

Metals: 

Cast  iron 0. 1298 

Wrought  iron 0. 1138 

Softsteel 0.1165 

Copper 0.0951 

Brass.... 0.0939 

Tin 0.0569 

Lead 0.0314 

Aluminum 0.2185 

Zinc 0.0953 

Mercury 0.0333 

Minerals: 

Coal 0.2777 

Marble 0.2159 

Chalk 0.2149 

Stones  generally 0.2100 

Limestone 0 . 2170 

Building  Materials: 

Brickwork 0. 1950 

Masonry 0 . 2000 

Plaster 0.2000 

Pine  wood 0.4670 

Oak  wood 0.5700 

Birch 0.4800 

Glass..  .  0.1977 


SPECIFIC  HEAT  OF  GASES 

Constant  Constant 

Substance                                                   pressure  volume 

Air 0.2415  0.1729 

Oxygen 0.2175  0.1550 

Hydrogen 3.4090  2.4122 

Nitrogen 0.2438  0. 1727 

Steam 0.5000  0.3500 

Carbonic  acid,  CO2 0.2479  0.1758 

Ammonia 0 . 5080  0 . 2990 

Example. — It  is  required  to  raise  the  temperature  of  a  cast-iron"radiator  ^ 
weighing  300  pounds  from  70°  to  212°.     The  temperature  through  which 
the  iron  would  be  raised  would  be  212°  minus  70°  or  142°.     From  Table 


HEAT 

II  we  see  that  to  raise  1  pound  of  cast  iron  JL°  would  require  0.1298 
"units.  To  raise  1  pound  142°  would  require  142  times  0.1298  or  18.43  heat 
units,  and  to  raise  300  pounds  1°  would  require^  300  times  this  amount  or 
5529  B.t.u.,  the  heat  required  to  heat  the  radiator.  "•^ 

Example. — A  church  80  by  100  feet  inside  and  30  feet  high,  to  the  eaves 
has  stone  walls  2^  feet  thick  for  10  feet  above  the  ground  and  for  the 
remaining  distance  2  feet  thick.  The  roof  has  a  slope  of  45  degrees  and  is 
made  of  2  by  8-inch  oak  rafters,  16  inches  on  centers,  covered  with  1  inch 
of  oak  boarding,  tar  paper  and  slate  Y±  inch  thick.  Main  floor  composed 
of  two  1-inch  thicknesses  of  boards  laid  on  2  by  12-inch  joists,  16-inch  centers. 
Ceiling  is  of  plaster  %  inch  thick.  The  church  has  20  windows,  6  feet  wide 
and  15  feet  high,  12  windows  4  feet  wide  and  6  feet  high,  and  2  doors,  8  feet 
wide  and  12  feet  high.  Allowing  an  addition  of  15  per  cent,  for  furnishings, 
find  the  heat  required  to  raise  the  temperature  of  the  structure  from  0° 
to  50°. 

Weight  of  stonework,  stone  weighing  160  pounds  per  cubic  foot:  *• 

370  X  10  X  2K  =    9,250  cubic  feet 

368  X  20  X  2  =  14,720  cubic  feet 

84^2X40X2X2  =    6,720  cubic  feet  *** 


30,690  cubic  feet 

Deduction  for  windows  and  doors: 

20  X  6  X  15  X  2       =  3,600 

12  X  4  X    6  X  2       =     576 

2  X  8  X  12  X  2H   =     480 

4,656         4,656 


26,034  X  160  =  4,165,440  pounds. 
Weight  of  woodwork,  weight  per  cubic  foot  taken  as  40  pounds  : 

o  vx  o 

^f~  X  56.2  X  75  X  2  X  40    =  37,500  pounds  of  rafters. 

-L4'± 

56.2  X  104  X  2  X  Y\i  X  40     =  39,000  pounds  of  roof  boards. 
80  X  100  X  %  2  X  40  .  =  53,300  pounds  of  floor  boards. 

*        X  80  X  75  X  40  =  40,000  pounds  of  floor  joists. 


Total  weight  of  woodwork         =  169,800  pounds. 
Slate,  weight  per  cubic  foot  taken  as  170  pounds: 

56.5  X  104  X  2  X  Y±%  X  170  =  41,600  pounds. 
Plaster,  weight  per  cubic  foot  taken  as  90  pounds  : 

(360X30+80X40  +  100X56.5  X2)MXK2X90  =  142,300  pounds. 
Air,  weight  per  cubic  foot  taken  as  0.08  pounds: 

(80  X  30  X  100  +  M  X  80  X  40  X  100)  0.08  =  32,000  pounds. 
Heat  required  : 


HEATING  AND  VENTILATION 

4,165,440  X  50  X  0.2100  =  43,737,000  B.t.u. 
169,800  X  50  X  0.5700  =  4,839,000  B.t.u. 

41,600  X  50  X  0.2159  =  449,000  B.t.u. 
142,300  X  50  X  0.2000  =  1,423,000  B.t.u. 

32,000  X  50  X  0.2415  =       386,000  B.t.u. 

50,834,000  B.t.u. 
Adding  15  per  cent,  for  furnishings   7,625,000  B.t.u. 


Total  to  raise  to  50°  58,459,000  B.t.u. 

The  heating  of  the  building  structure  may  be  very  important  in  determining 
the  size  of  the  heating  plant  when  a  building  is  intermittently  heated. 

7.  First  Law  of  Thermodynamics. — When  mechanical  energy 
is  produced  from  heat  a  definite  quantity  of  heat  is  used  up 
for  every  unit  of  work  done  and,  conversely,  when  heat  is  pro- 
duced by  the  expenditure  of  mechanical  energy  the  same  definite 
quantity  of  heat  is  produced  for  every  unit  of  work  spent.  This 
first  law  of  thermodynamics  might  also  be  called  the  law  of  the 
Conservation  of  Energy.  The  relation  between  work  and  heat 
has  recently  been  determined  with  great  accuracy  and  the 
results  show  that  one  British  thermal  unit  is  equivalent  to  778 
foot-pounds.  This  factor  is  called  the  mechanical  equivalent 
of  heat  or  Joule's  equivalent. 

Problems 

1.  Convert  50°F.  to  degrees  Centigrade.     Convert   150°C.   to  degrees 
Fahrenheit.     Convert  219°F.  to  degrees  Centigrade.     Convert  225°F.  to 
absolute  temperature  on  the  Fahrenheit  scale. 

2.  A  copper  ball  weighing  10  pounds  is  heated  in  a  fire  and  immediately 
placed  in  a  vessel  of  water  having  an  equivalent  water  weight  of  10  pounds. 
The  water  is  raised   in   temperature  from  50°  to  100°.     What  was  the 
temperature  of  the  ball  when  it  was  removed  from  the  fire? 

3.  A  bar  of  cast  iron  weighing  5  pounds  and  at  a  temperature  of  250°F. 
and  a  bar  of  lead  weighing  10  pounds  and  at  a  temperature  of  300°  are  put 
into  a  tub  of  water  which  is  at  120°.     The  water  is  heated  to  123°.     Neglect- 
ing the  effect  of  the  tub  itself  and  the  heat  lost  during  the  process,  how 
much  water  is  in  the  tub? 

4.  A  piece  of  limestone  weighing  10  pounds  and  at  a  temperature  of 
150°F.  and  a  piece  of  wrought  iron  weighing  20  pounds  and  at  a  temperature 
of  70°  are  put  into  a  tank  and  a  sufficient  quantity  of  water  at  88°  is  added 
to  bring  the  temperature  of  the  water,  stone,  and  iron  to  90°.     How  much 
water  is  required,  neglecting  the  heat  lost  during  the  process? 


CHAPTER    II 
HEAT  LOSSES  FROM  BUILDINGS 

8.  Sources  of  Heat  Loss. — When  the  interior  of  any  building 
is  maintained  at  a  temperature  higher  than  that  of  the  outside 
air  there  is  a  continual  loss  of  heat  from  the  building.       The 
functions  of  a  heating  system  are,  first,  to  raise  the  temperature 
of  the  interior  of  the  building  to  the  point  desired  and,  second, 
to  maintain  this  temperature  by  supplying  sufficient  heat  to 
replace  that  lost  from  the  building.     The  determination  of  the 
amount  of  heat  lost  from  the  building  under  maximum  condi- 
tions is  the  first  step  in  designing  the  heating  system. 

Before  taking  up  the  methods  of  calculating  heat  loss  it  is 
necessary  to  consider  first  the  manner  in  which  heat  may  be  given 
up  by  any  body.  There  are  three  ways  in  which  heat  can  be 
transmitted  from  a  solid  body:  byjajiiatioj^  by  conduction,  and 
by  convection.  Each  of  these  will  be  discussed  separately. 

9.  Radiation. — Heat  is  transmitted,  or  radiated,  through  space 
by  what  is  supposed  to  be  a  motion  or  vibration  of  the  ether  which 
is  believed  to  pervade  all  space.     Radiant  heat  follows  the  same 
physical  laws  as  radiant  light,   being  radiated,   like  light,  in 
straight  lines.     We  may  have  heat  "shadows"  just  as  we  have 
light  'shadows  and  as  with  light  the  intensity  of  radiant  heat  is 
inversely  proportional  to  the  square  of  the  distance  from  the 
source. 

Some  substances  are  transparent  to  heat  rays  and  others  absorb 
them.  Gases  are  almost  perfectly  transparent  to  radiant  heat 
while  such  substances  as  wood,  hair  felt,  and  mineral  wool  are 
almost  perfectly  opaque  to  it.  Radiant  heat  does  not  affect 
the  medium  through  which  it  passes.  When  heat  is  radiated 
fErough  the  atmosphere  for  example,  the  atmosphere  is  not 
perceptibly  warmed  by  it. 

The  rate  at  which  heat  is  radiated  increases  as  the  absolute  tem- 
perature of  its  source  is_.,raised.  It  has  been  determined  experi- 
mentally that  the  amount  of  heat  radiated  from  a  body  varies 
as  the  4th  power  of  the  absolute  temperature,  or 


1.1 


10 


HEATING  AND  VENTILATION 


in  which  Qr  is  the  quantity  of  heat  radiated,  T  the  absolute  tem- 
perature of  the  body,  and  K  a  constant  depending  upon  the  nature 
of  the  substance  composing  it.  Radiant  heat  is  given  off  by  all 
bodies,  the  net  amount  of  heat  radiated  by  a  body  being  the 
difference  between  the  total  amount  radiated  from  it  and  the 
amount  radiated  from  other  bodies  which  is  absorbed  by  it. 
If  one  body  of  absolute  temperature  T^  is  surrounded  by  another 

<  body  of  the  same  material  at  temperature  T2,  then  the  heat  which 

1  will  pass  between  them  is 


Qr  = 


This  is  known  as  Stefan's  law. 


-  TV) 


FIG.  2. 


10.  Conduction.  —  As  has 
already  been  stated,  heat  will 
pass  from  any  body  to  a  body 
at  a  lower  temperature  which 
is  brought  into  contact  with 
it.  It  is  further  true  that  if 
one  part  of  a  body  is  at  a 
higher  temperature  than  an- 
other part  there  will  be  a  flow 
of  heat  through  the  body. 
The  transmission  of  heat  in 
this  manner  is  known  as 
conduction,  A  familiar  ex- 
ample of  this  phenomenon  is 
the  flow  of  heat  along  an  iron  bar,  one  end  of  which  is  heated  in 
a  fire.  The  ability  of  different  materials  to  conduct  heat  differs 
considerably.  Metals  are  the  best  conductors  of  heat,  while  such 
materials  as  wood,  felt,  asbestos,  etc.,  are  very  poor  conductors. 

The  specific  conductivity  of  a  material  is  the  amount  of  heat 
which  would  be  conducted  through  a  plate  of  the  material  of 
unit  area  and  unit  thickness  with  a  unit  difference  in  temperature 
between  the  two  sides  of  the  plate. 

The  conduction  of  heat  which  takes  place  through  the  walls  of 
a  building  may  be  best  understood  from  Fig.  2  in  which  PP  is  a 
plate,  one  side  of  which  is  enclosed  by  the  walls  Tf  W.  Let  the 
temperature  of  the  outside  of  the  plate  be  59°  and  let  60°  be  the 
temperature  of  the  inside  of  the  plate,,  of  the  inside  walls  TFTF, 
and  of  the  inside  air.  Then  all  the  heat  that  is  lost^y  the  room 
must  be  lost  by  conduction  through  the  plate  PP.r  The  amount 


HEAT  LOSSES  FROM  BUILDINGS  11 

of  heat  lost  will  be  dependent  upon  the  material  of  the  plate  PP, 
upon  the  difference  in  temperature  of  its  two  sides,  and  upon  its 
thickness. 

Let  e  =  the  specific  conductivity  of  the  material  in  B.t.u.  per__ 
hour,  pej^qjiarejoot  of  area,  pejjn^^injy^^ne^pej: 


ti  =  tne  temperature  of  the  warmer  side  of  the  plate,  in 

degrees  F. 
tz  =  the  temperature  of  the  cooler  side  of  the  plate,  in 

degrees  F. 

A  =  the  area  of  surface  in  square  feet. 
I  =  the  thickness  of  plate  in  inches. 
Q  —  the  total  quantity  of  heat  transmitted  in  B.t.u.  per 

hour. 
Then 


Q  = 

Ae 
the  conductivity  of  the  heat  path  is  then  -y-  and  the  resistance 


of  the  heat  path  is  its  reciprocal    .   . 

Example. — Suppose  a  boiler  plate,  5  feet  square,  and  %  inch  thick,  to 
have  a  temperature  of  70°  on  one  side  and  200°  on  the  other  side.  Assume 
the  specific  conductivity  of  the  metal  to  be  240  B.t.u.  per  hour  per  square 
foot  of  area  per  inch  in  thickness  per  degree  difference  in  temperature. 
The  total  heat  transmitted  per  hour  is  then 

Q  ,J«XMO(200-70)  _  ij560)0oo  fi  t  ^  per  ^^^ 

11.  Convection. — When  a  body  is  in  contact  with  a  fluid 
at  a  lower  temperature,  the  envelope  of  fluid  surrounding  it 
becomes  heated  by  conduction  of  heat  from  the  body.  As  this 
fluid  envelope  is  heated  its  density  decreases  and  it  is  forced  to 
rise,  giving  place  to  the  colder  fluid  from  below.  A  continuous 
current  is  thus  created  and  maintained  over  the  surface  of  the 
body.-  This  process  of  heat  transfer  is  called  convection.  It 
should  be  noted  that  the  heat  actually  leaves  the  hot  body  by  con- 
duction from  its  surface  to  the  fluid  in  contact  with  it.  The 
essential  characteristic  of  the  process  of  convection  is  the  con- 
tinuous renewal  of  the  fluid  layer  at  the  surface  of  contact. 

The  loss  of  heat  from  a  body  by  convection  is  independent  of 
the  material  composing  it,  but  is  greatly  affected  by  the  form  of 
the  body,  a  cylinder  and  a  sphere,  .for  example,  transmitting 
different  amounts  of  heat  by  convection  per  square  foot  of  sur- 


12  HEATING  AND  VENTILATION 

face.  The  velocity  of  the  fluid  over  the  surface  also  affects  the 
rate  of  heat  transmission.  In  the  case  of  convection  by  air  the  air 
movement  is  often  produced  by  some  external  force,  as  when  the 
wind  blows  against  a  building  or  when  a  fan  in  an  indirect  heating 
system  forces  air  over  the  surface  of  steam  coils.  An  increase 
in  the  velocity  produces  a  more  frequent  renewal  of  the  layer  of 
air  in  contact  with  the  body  and  augments  the  rate  of  heat 
transmission. 

Heat  may  also  be  transmitted  from  a  fluid  to  a  solid  by  con- 
vection as  well  as  from  a  solid  to  a  fluid.  An  example  of  this 
process  is  the  transfer  of  heat  from  the  warm  air  of  a  room  to  the 
cold  outside  walls.  The  air,  upon  giving  up  its  heat,  increases  in 
density  and  falls,  giving  place  to  warmer  air  from  above  and 
producing  a  continuous  downward  current. 

12.  Loss  of  Heat  from  Buildings. — The  heat  which  is  lost 
/from  a  building  may  be  divided  into  two  parts :  (a)  the  heat  which 
/  passes  by  conduction  through  the  building  structure;  and  (6) 
the  heat  which  is  lost  due  to  air  passing  into  and  out  of  the 
building.     The  latter  may  consist  merely   of  the  natural  in- 
filtration through  the  building  structure,  or  may  be  partly  due 
to  air  supplied  for  ventilation. 

The  heat  which  flows  by  conduction  through  the  walls,  floors, 
roof,  etc.  is  transmitted  from  the  outer  surfaces  which  are  exposed 
to  air  partly  by  radiation  and  partly  by  convection.  From  the 
surfaces  buried  in  the  ground — the  basement  walls  and  floors — it 
is  dissipated  by  conduction  into  the  earth.  The  calculation  of 
the  heat  lost  by  convection  is  very  difficult.  Methods  of  arriving 
at  the  loss  by  convection  from  bodies  of  various  shapes  were 
developed  by  Peclet  and  are  given  in  Box's  "  Treatise  on  Heat," 
but  these  methods  cannot,  as  a  rule,  be  applied  to  the  loss  of  heat 
from  buildings.  They  assume,  for  example,  that  the  air  surround- 
ing the  object  is,  except  for  the  influence  of  the  heat  from  the 
body  itself,  in  a  perfectly  quiescent  state.  In  the  case  of  buildings 
this  is  far  from  true,  for  the  air  surrounding  a  building  is  always 
circulated  more  or  less  rapidly  by  the  winds.  Because  of  the 
necessity  of  taking  into  account  variable  factors  of  this  nature, 
the  heat  loss  from  a  building  could  not  be  stated  in  any  simple 
expression  and  the  practical  rules  that  are  used  for  such  calcula- 
tions are  therefore  largely  empirical.  The  common  method  of 
treating  the  loss  of  heat  through  building  walls  as  given  in  th£ 
following  pages  was  translated  by  J.  H.  Kinealy  from  the  work 
of  Rietschel  and  published  in  the  Metal  Worker. 


HEAT  LOSSES  FROM  BUILDINGS 


13 


In  the  simplest  form  of  building  the  walls  consist  of  one  solid 
piece  of  a  single  material  and  the  transmission  of  heat  takes  place 
from  the  air  of  the  room  to  the  inner  surface  of  the  wall  by 
convection,  through  the  wall  by  conduction,  and  from  the  outer 
surface  of  the  wall  by  convection  and  by  radiation.  Such  a 
wall  is  shown  in  Fig.  3.  In  order  that  heat  may  flow  through  the 
wall  it  is  necessary  that  the  room  temperature  t\  be  higher  than 
the  temperature  of  the  inside  of  the  wall  ti,  that  the  temperature 
of  the  outside  of  the  wall  to'  be  lower  than  t\\  and  that  the  tem- 
perature of  the  outside  air  to  be  lower  than  t0f.  The  amount  of 
heat  which  will  be  transferred  from  the  air  of  the  room  to  a  unit 


Fig  .3 


x^xSsxvi/v' 

*$ 

Fig.4 


/o 


*>. 


Fig.5 


area   of  the  wall  will  be  a\   (ti  —  t\)  in  which  a\  is  a  constant. 
The  amount  of  heat  flowing  through  a  unit  area  of  the  wall  will 


be  - 


(ti'-to')  in  which  e\  is  a    constant  which  represents  the 

specific  conductivity  of  the  material  composing  the  wall.  Simi- 
larly the  heat  transfer  from  a  unit  area  of  the  outside  wall 
surface  is  do  (to'  —  to). 

When  the  rate  of  heat  flow  through  the  wall  has  reached  a 
stable  condition  the  quantity  of  heat  flowing  through  successive 
points  of  the  walls  thickness  must  be  the  same  and  we  have 
therefore, 

oi(<i  -  ti)  =  ~(ti   -  <o')  =  «o(*o'  -  «o) 

A  wall  may  be  made  up  of  a  series  of  layers  of  different  mate- 
rials, as  shown  in  Fig.  4.  The  transmission  of  heat  takes  place 
in  the  same  way  except  that  the  conductivity  of  the  successive 
layers  may  be  different.  In  a  wall  such  as  shown  in  Fig.  5  the 
heat  passes  through  the  inside  wall  to  the  air  in  the  air  space 
and  thence  through  the  outside  wall  to  the  outside  air,  the 
temperature  at  each  successive  point  from  the  inside  to  the  out- 


14  HEATING  AND  VENTILATION 

feide  being  lower,  as  before.  The  temperature  gradient  or  fall 
throughout  the  thickness  of  the  wall  is  shown  by  the  heavy  line  in 
Figs.  3,  4,  and  5. 

An  air  space  as  illustrated  in  Fig.  5  is  of  value  in  decreasing  the 
conductivity  of  the  wall,  at  the  temperatures  met  with  in  heating 
work.  Heat  is  transmitted  through  the  air  space  by  radiation 
and  by  convection.  The  amount  of  radiant  heat  transmitted 
will  increase  as  the  temperatures  of  the  surfaces  rise,  since  it 
varies  as  the  fourth  power  of  the  absolute  temperatures  (Par.  9). 
Consequently  the  value  of  an  air  space  as  an  insulator  is  not  great 
at  high  temperatures,  as  in  furnace  walls. 

If  ai,  «2,  «3  and  a0  are  the  constants  representing  the  con- 
ductivity of  heat  between  the  air  and  the  wall  surfaces  (Fig.  5) 
and  61  and  ez  are  the  'specific  conductivities  of  the  materials  com- 
posing the  two  walls,  then  the  heat  transmitted  through  the  wall 
may  be  expressed  as  in  the  previous  case,  as  follows  : 


'  -  tQ) 

z 

In  order  to  use  these  expressions  it  would  be  necessary  to  know 
the  temperature  of  all  the  wall  surfaces.  These  temperatures 
are  not  known.  The  only  known  temperatures  are  the  tempera- 
tures of  the  air  inside  the  room  and  of  the  air  outside  of  the  build- 
ing. Therefore,  let  us  assume  that  the  heat  transmission  through 
the  wall  may  be  represented  by  the  expression  k(ti  —  to),  in  which 
k  is  a  constant  to  be  determined.  We  then  have  for  Fig.  3: 

k(ti  -  to)  =  ai(*i  -  ti')  =  -  fa'  -  t0')  =  aQ(to'  -  to) 

x 

And  for  Fig.  5: 

^  (t,f  -  t2f)  =  a2(*2'  -  «2) 

-  (t*"  -  U')  =  a0(tv'  -  to) 

X2 

Solving  for  k  we  have,  for  Fig.  3: 

ti  -  IS  =       kfa  -  t0) 


k(tl  - 


HEAT  LOSSES  FROM  BUILDINGS  15 

Adding  these  three  equations  and  simplifying, 

•fc-T_i_I  (i) 

d\          C\        Q>Q 

And  for  Fig.  5: 


i+j+i+i+j+i 

/>» 

For  thin  glass  or  thin  metal  walls  -  is  a  very  small  quantity  and 

6 

may  often  be  neglected. 

The  values  of  a  and  e  must  be  known  before  k  can  be  deter- 
mined. The  value  of  the  convection  factor,  a,  is  determined  by 
Grashof  by  the  following  equation: 

a = c  + d+ 


10,000 

in  which  c  is  a  factor  depending  on  the  condition  of  the  air, 
whether  at  rest  or  in  motion.  Rietschel  gives  the  following 
values  for  c: 

TABLE  III. — VALUES  OF  c 

c 

Air  at  rest,  air  in  rooms 0 . 82 

Air  with  slow  motion,  air  in  rooms  in  contact  with 

windows 1 . 03 

Air  with  quick  motion,  air  outside  of  a  building 1 . 23 

The  factor  d  depends  upon  the  material  composing  the  wall  and  on  the  con- 
dition of  the  surface.  The  values  for  d  may  be  taken  as  follows: 

TABLE  III. — VALUES  OF  d 

Substance  d  Substance  d 

Brickwork 0.740  Sheet  iron 0.570 

Mortar  and  similar  materials  0 . 740  Sheet  iron  polished 0 . 092 

Wood 0.740  Brass  polished 0.053 

Glass 0.600  Copper 0.033 

•  Cast  iron. .  .  v 0.650  Tin 0.045 

Paper .' 0.780  Zinc 0-049 

T  is  the  difference  between  the  temperature  of  the  air  and  that 
of  the  surface  of  the  wall.  For  walls  composed  of  materials  of  low 
conductivity  or  very  thick  walls  it  may  be  taken  as  zero.  In 
approximate  calculations  it  is  usually  taken  as  zero. 


16  HEATING  AND  VENTILATION 

The  following  values  of  T  are  given  by  Rietschel: 

TABLE  IV.  —  VALUES  OF  T 

Brickwork    5  inches  thick  ..........                          .....  14  .  4 

Brickwork  10  inches  thick  ...........................  12  .  6 

Brickwork  15  inches  thick  ..........                            ....  10  .  8 

Brickwork  20  inches  thick  ...........                          ----  9.0 

Brickwork  25  inches  thick  ...........................  7.2 

Brickwork  30  inches  thick  ...........................  5.4 

Brickwork  40  inches  thick.  ;  .........  1.8 

For  single  windows  .....................                    ...  36  .  0 

For  double  windows  .............................  18  .  0 

For  wooden  doors  ..................                            •  •  •  1.8 

Table  V  gives  values  of  e.  These  values,  as  given  by  different 
authorities,  vary  considerably. 

TABLE  V.  —  VALUES  OF  e 

e 

Brickwork  .......................................  5.  60 

Mortar,  plaster  ...................................  5  .  60 

Rubble  masonry  ..................................  14  .  00 

Limestone  ........................................  15  .  00 

Marble,  fine-grained  ...............................  28  .  00 

Marble,  coarse-grained  ..........  '.  ........  -  .........  22  .  00 

Oak  across  the  grain  ..............................  1-71 

Pine,  with  the  grain  .............................  1  .  40 

Pine,  across  the  grain  ..............................  0  .  76 

Sandstone  ........................................  10.00 

Glass  ...........................................  6.60 

Paper  ...........................................  0.27 

For  example,  assume  a  brick  wall  as  shown  in  Fig.  6.  There 
are  four  air  contact  surfaces  and  two  walls  through  which  conduc- 
tion takes  place,  then: 

k  is  the  same  as  in  equation  (2)  . 

Rietschel  assumes  01,  a2,  and  a3  equal  and  he  uses  the  same 
value  of  T  as  for  a  solid  of  thickness  equal  to  the  brickwork  with- 
out the  air  space. 

ai  =  a2  =  03  =  0.82  +  0.74  +  (40X0.82  +  30X0.74)10  =  ^ 

lU,uul) 

o.  =  1.23  +  0.74  +  MX-23  +  30X0.74)10 


l(j,uuU 


HEAT  LOSSES  FROM  BUILDINGS 

Since  both  walls  are  of  brickwork 
xi       4.75 


17 


5.6 


=  0.85 


8.25  " 


5.6 


=  1.47 


Substituting  in  equation  (2) 


f  _  __  _ 
0.62  +  0.85  +  0.62  +  0.62  +  1.47  +  0.49 

Making  this  same  calculation,  assuming  T  =  0,  gives 
k  =  0.210 


014 


13.  Experimental  Determination  of  Coefficients. — The  method 
outlined  in  the  preceding  paragraph  is  useful  in  computing 
the  heat  loss  for  unusual  types  of  walls.  The  value  of  the 
coefficient  k  has  been  determined  for  most  of  the  ordinary  types 
of  wall  construction  by  experiment. 

The  method  most  commonly  used  in  making  such  determina- 
tions is  to  employ  a  cubical  box,  having  five  faces  made  of  a 
material  of  low  conductivity,  the  sixth  side  being  constructed 
of  the  material  to  be  tested.  The  temperature  inside  of  the  box 
is  maintained  constant  and  above  that  of  the  surrounding  air, 
by  supplying  a  measured  amount  of  heat,  usually  electrically,  to 
the  interior.  'With  the  proper  corrections  made  for  the  loss 
through  the  other  five  sides,  the  heat  transfer  through  the  mate- 
rial under  test  can  be  accurately  determined. 

In  Table  VI  are  given  the  values  of  k  for  several  common  types 
of  building  construction. 


18  HEATING  AND  VENTILATION 

TABLE  VI. — COEFFICIENTS  OF  HEAT  TRANSMISSION  FOR  VARIOUS 

MATERIALS 

k 

B.t.u.  per  square  foot, 
per  hour  per  degree 

difference   in 
Walls:  temperature 

Brick  wall  4  inches  thick,  plain 0 . 52 

Brick  wall  8^  inches  thick,  plain 0 . 37 

Brick  wall  4  inches  thick,  furred  and  plastered 0 . 28 

Brick  wall  8%  inches  thick,  furred  and  plastered 0.23 

Concrete  wall  4  inches  thick,  furred  and  plastered 0.31 

Concrete  wall  6  inches  thick,  furred  and  plastered 0 . 30 

Clapboard  wall  with  paper,  sheathing,  studding,  and 

lath  and  plaster 0.23 

Ceilings  and  Roofs: 

Lath  and  plaster,  no  floor  above 0 . 32 

Lath  and  plaster,  single  floor  above 0 . 26 

Tin  or  copper  roof  on  1-inch  boards 0 . 45 

Shingle  roof 0 . 33 

Windows,  Skylights  and  Doors: 

Ordinary  windows 1 . 09 

Double  windows 0 . 45 

Single  skylight 1 . 50 

Pine  door  %  inch  thick 0. 47 

Oak  door  %  inch  thick 0.63 

More  complete  tables  are  given  in  the  Appendix. 

14.  Temperatures  Assumed  in  Heating. — In  determining  the 
heat  transmission  through  the  walls  of  a  building,  it  is  necessary 
to  assume  certain  temperatures  for  the  outside  air  and  for  the 
inside  air.  In  the  latitude  of  New  York  City  it  is  customary  to 
assume  0°  for  the  outside  temperature.  In  the  latitude  of 
Washington  it  is  customary  to  assume  20°  above,  and  in  the 
latitude  of  St.  Paul  20°  below.  The  assumed  outside  tempera- 
ture is  ordinarily  taken  as  the  temperature  which  might  exist 
for  a  period  of  at  least  24  hours.  Lower  temperatures  than  these 
may  exist  for  short  periods  but  the  heat  stored  in  the  building 
structure  is  usually  sufficient  to  counteract  this  effect.  The 
inside  temperature  to  be  assumed  depends  upon  the  type  of 
building.  The  temperature  maintained  in  many  classes  of 
buildings  is  largely  a  matter  of  custom.  In  residences  this  tem- 
perature is  higher  in  the  United  States  than  in  any  other  country 
in  the  world,  with  the  possible  exception  of  Germany.  In 
England  and  many  other  countries  a  temperature  of  from  55°  to 
60°  is  a  perfectly  proper  temperature  for  a  room;  while  in  this 
country  ,the  temperature  ordinarily  ranges  from  65°  to  70°. 


HEAT  LOSSES  FROM  BUILDINGS  19 

The  following  are  the  inside  temperatures  usually  assumed: 
TABLE  VII.  —  INSIDE  TEMPERATURES 

Degrees 

Residences  .....................................  70 

Lecture  rooms  and  auditoriums  ...................  65 

Factories  for  light  work  ..........................  65 

Factories  for  heavy  work  ........................  60 

Offices  and  schools  .......................  /  ......  68  to  70 

Stores  .........................................  65 

Prisons  ........................................  65 

Bathrooms  .......................  "  ..............  72 

Gymnasiums  ...................................  55  to  60 

Hot  houses  .....................................  78 

Steam  baths  ...................................  .  110 

Warm  air  baths  .................................  120 

The  following  assumptions  are  ordinarily  made  for  unheated 
spaces: 


Degrees 

Cellars  and  closed  rooms  .........................  32 

Vestibules  frequently  opened  to  the  outside  ........  32 

Attics  under  a  roof  with  sheathing  paper  and  metal 

or  slate  covering  ..............................  25 

Attics  under  a  roof  with  paper  sheathing  and  tile 

covering  .....................................  32 

Attics  under  a  roof  with  composition'  covering  ......  40 


15.  Heat  Lost  Due  to  Infiltration.—  No  building  is  ever  air- 
tight; there  is  a  large  amount  of  leakage  through  the  walls,  the 
windows,  and  other  openings.  The  amount  of  this  infiltration 
depends  largely  upon  how  well  the  building  'has  been  constructed 
and  upon  the  type  of  construction.  For  this  reason  no  definite 
rule  can  be  given  for  the  determination  of  infiltration,  and  the 
allowance  made  for  this  loss  must  be  a  matter  of  judgment  and 
experience.  Usually  the  volume  of  infiltration  is  expressed  as  a 
certain  ratio  of  the  cubic  contents,  and  experiments  go  to  show 
that  the  air  of  the  average  room  is  changed  about  once  an  hour 
because  of  infiltration.  In  rooms  where  doors  are  frequently 
opened  to  the  outside,  or  where  the  windows  are  loosely  fitted 
"and  the  construction  is  faulty,  the  change  of  air  may  be  as  fre- 
quent as  twice  an  hour. 

Strictly  speaking  the  amount  of  infiltration  does  not  de- 
pend upon  the  volume  of  the  room  but  upon  the  nature  and 


20  HEATING  AND  VENTILATION 

size  of  the  windows.  Experiments1  have  shown  that  the  amount 
of  air  leakage  varies  considerably  for  different  types  of  windows. 
Some  forms  of  metal  sash  allow  a  large  amount  of  leakage  to 
take  place.  Weather  strips  are  very  effective  in  reducing  air 
leakage.  As  the  principal  source  of  leakage  is  around  the  window 
sash  the  amount  of  leakage  may  be  considered  as  varying  directly 
with  the  perimeter  of  the  windows.  It  is  customary  to  assume 
a  leakage  of  from  1.0  to  1.5  cubic  feet  of  air  per  minute  per  foot 
of  sash  perimeter  for  windows  equipped  with  weather  strips. 
For  windows  without  weather  strips  a  considerably  higher  factor 
should  be  used.  In  large  buildings  the  amount  of  infiltration 
should  be  computed  in  this  manner,  especially  in  the  case  of  a  tall 
or  exposed  building. 

In  very  tall  buildings  there  is  often  a  pronounced  chimney 
effect  in  the  building  itself,  especially  if  there  are  open  elevator 
shafts  or  stair  wells. 

The  heat  required  to  supply  these  infiltration  losses  must  be 
sufficient  to  warm  the  air  from  the  temperature  of  the  outside 
air  to  that  of  the  room/  If  the  infiltration  is  figured  on  the  basis 
of  a  certain  number  of  air  changes  per  hour  the  loss  from  this 
source  may  be  expressed  as  follows: 

Let  Ha  =  heat  required  per  hour  to  supply  loss  due  to  infiltration. 
C  =  cubic  contents  of  the  room. 
n  =  number  of  changes  per  hour. 
tr  =  temperature  of  the  room. 
tQ  =  temperature  of  the  outside  air. 

„     _  C(tr  -  tQ)n 
Ha= 


55.2 
The  factor  55.2  =      9415  X  0  074Q  =  number  of  cubic  feet 

of  air  which  1  B.t.u.  will  raise  1°  where  0.2415  is  the  specific 
heat  of  air  at  constant  pressure  and  0.0749  is  the  weight  of  a 
cubic  foot  of  air  at  70°. 

16.  Heat  Required  for  Ventilation.  —  The  heat  required  for 
ventilation  can  easily  be  computed  when  the  amount  of  air 
supplied  per  hour  is  known. 

^ee  "Window  Leakage"  by  S.  F.  VOOBHEES  and  H.  C.  MEYER,  Trans. 
A.  S.  H.  &  V.  E.,  1916. 


HEAT  LOSSES  FROM  BUILDINGS  21 

Let  H  =  heat  required  for  ventilation,  B.t.u.  per  hour. 
Q  =  quantity  of  air  supplied  in  cubic  feet  per  minute. 

Then, 

„       60  X  Q(tr  -  t0] 
~~5£2~~ 

Besides  supplying  heat  to  replace  that  lost  through  the  walls 
and  by  infiltration  of  air,  a  heating  system  must  supply  the  heat 
which  is  stored  in  the  structure  and  its  contents  and  in  the  inside 
air.  In  heavy  buildings  the  effect  of  the  heat  stored  in  the  walls 
may  have  a  material  effect  upon  the  amount  of  heat  which  must 
be  supplied  to  warm  the  building  initially.  If  the  building  is 
intermittently  heated  the  effect  is  decidedly  appreciable.  The 
best  illustration  is  in  the  cathedrals  of  Europe  in  which  no  heating 
systems  are  used  and  the  heat  stored  in  the  walls  during  the 
summer  serves  to  keep  the  building  warm  throughout  the  year. 

The  heat  which  is  required  initially  to  warm  the  inside  air  and 
the  building  structure  affects  the  rapidity  with  which  the  build- 
ing can  be  heated,  to  the  desired  temperature.  It  is  often 
desirable  to  investigate  this  question  in  designing  a  heating 
system  which  is  to  be  operated  intermittently  and  to  increase  the 
capacity  of  the  heating  system,  if  necessary,  so  that  the  build- 
ing can  be  warmed  within  a  reasonable  time. 

17.  Calculation  of  Heat  Loss  from  a  Building. — In  deter- 
mining the  heat  loss  from  a  room  all  surfaces  should  be  considered 
which  have  on  the  outside  a.  lower  temperature  than  the  tem- 
perature to  be  maintained  in  the  room.  If  the  room  is  over  a 
portion  of  the  basement  which  is  unheated  or  below  an  unheated 
attic,  the  loss  through  the  floor  or  ceiling  should  be  considered. 
Similarly,  if  an  adjacent  room  is  liable  to  be  unheated  at  times, 
the  additional  heat  loss  through  the  wall  should  be  taken  into 
account.  Ordinarily  it  is  assumed  that  there  is  no  loss  through 
inside  walls  where  the  surrounding  rooms  are  heated. 

The  conditions  under  which  the  room  is  to  be  used  should  be 
studied  in  determining  the  amount  of  heat  necessary.  In  certain 
rooms  such  as  restaurants  in  the  basements  of  buildings,  for  ex- 
ample, where  there  are  no  outside  windows,  the  problem  is  often 
one  of  cooling  rather  than  heating.  In  designing  any  heating 
system,  careful  consideration  should  be  given  to  the  conditions 
existing  such  as  the  use,  occupancy,  and  exposure  of  each  room 
in  the  building,  and  the  other  sources  of  heat  therein,  if  any. 

The  first  step  in  computing  the  heat  loss  is  to  determine  for 


22  HEATING  AND  VENTILATION 

every  room  the  gross  surface  of  exposed  wall,  and  the  window 
surface,  from  which  the  net  wall  surface  is  obtained  by  sub- 
traction. The  heat  loss  through  the  walls  can  then  be  computed 
from  the  expression, 

Hw  =  Wk(tr  -  to) 
in  which 

Hw  =  heat  loss  in  B.t.u.  per  hour. 
W  =  exposed  wall  surface  in  square  feet. 
tr  =  inside  temperature. 
to  =  outside  temperature. 
k  =  coefficient  of  heat  transmission. 

A  similar  expression  must  be  worked  out  for  the  walls,  ceilings 
and  floors  next  to  unheated  spaces.  The  value  of  tr  in  such  cases 
may  be  taken  from  Table  VII. 

The  heat  loss  through  the  glass  surface  is  computed  from  the 
expression, 

Hg  =  GK(tr  -  to) 

in  which  G  is  the  area  of  the  entire  window  opening  in  square  feet 
and  k  is  the  coefficient  of  heat  transmission  for  glass. 

The  heat  lost'  due  to  air  infiltration  is  next  determined  by  one 
of  the  methods  given  on  pages  19  and  20. 

The  total  heat  loss  from  the  room  in  B.t.u.  per  hour  is  then 

H    =   HW   ~T~  H  g   ~\~  Ha 

18.  Correction  Factors.  —  The  heat  losses  determined  by  this 
method  are  for  rooms  not  exposed  to  prevailing  winter  winds. 

It  is  common  practice  to  add  certain  percentages  to  the  com- 
puted heat  losses  on  the  exposed  sides  of  the  building.  Also, 
when  a  building  is  intermittently  heated,  an  allowance  should 
be  made  to  insure  that  the  building  can  be  heated  within  a  reason- 
able time.  The  correction  factors  commonly  used  are  given  in 
Table  VIII. 

TABLE  VIII.  —  FACTORS  FOR  EXPOSURE  AND  INTERMITTENT  HEATING 

Percentage 
to 


For    exposure  in  direction  of    prevailing    winter    winds  / 

(usually  north  and  northwest)  .....................  15 

Same,  severe  conditions  ..............................  20 

For  west  exposure  ...................................  10 

For  building   heated  during  the  day  only  and  closed 

at  night  .........................................  10 

For  buildings  heated  during  the  day  and  open  at  night  ....  1,0-15 

For  buildings  heated  intermittently'.  ..................  10-15 


HEAT  LOSSES  FROM  BUILDINGS 


23 


19.  Heat  Given  Out  by  Persons  and  Processes. — In  consider- 
ing the  amount  of  heat  necessary  to  heat  a  room  attention  must 
be  given  to  the  amount  of  heat  that  will  be  given  off  by  the 
occupants  of  the  room  or  by  the  processes  which  go  on  in  it.  •  But 
these  sources  of  heat  cannot  always  be  depended  upon,  as  it  may 
sometimes  be  necessary  to  heat  a  room  when  there  are  no  people 
in  it  or  when  the  processes  ordinarily  going  on  are  not  in  opera- 
tion. On  the  other  hand,  it  may  be  necessary  to  cool  the  room 
instead  of  heat  it.  Often  in  large  auditoriums  the  greatest 
source  of  hea\  in  a  room  are  the  people  in  it.  The  following 
table  show^the  heat  given  off  by  the  human  body  under  various/ 
'conditions  in  a  room  at  a  temperature  of  70°. 


TABLE  IX 


Adults  at  rest 

Adults  at  work 

Adults  at  violent  exercise . . . 

Children 

Infants 


B.t.u.  per  hour 

440 

450-600* . 
600-1200 

240 
63 


Example  1. — Assume  a  room,  as  shown  in  Fig.  7.  Let  the  temperature 
be  maintained  in  the  room  at  70°,  the  temperature  of  the  outside  air  be 
0°.  Let  the  walls  be  of  brick,  18  inches  thick,  plastered  on  the  inside,  the 


Note:  Windows  2-6'x  6-o' 
FIG.  7. 


windows  be  2>£  by  6  feet,  the  ceiling  of  the  room  be  10  feet  high.  Let  the 
room  be  on  the  second  floor  of  the  building,  the  rooms  above  and  below 
heated.  The  window  openings  are  2  X  2>^  X  6  =  30  square  feet.  The 


24  HEATING  AND  VENTILATION 

gross  wall  surface  is  20  X  10  =  200  square  feet.  The  net  wall  surface  is 
200  -  30  =  170  square  feet.  The  cubic  contents  is  20  X  14  X  10  =  2800 
square  feet.  Then  the  heat  lost  from  the  room  would  be  determined  as 
follows. 

Hw  =  170  X  0.24  (70  -  0)  =  2856 

Hg  =    30  X  1.09  (70   -  0)  =  2289 

„.  .  ^M  X  1.0  -  3551 
H    =  8696  B.t.u.  per  hour. 

Problems 

1.  Compute  the  value  of  k  for  a  wall  consisting  of  2  inch  pine  boards. 
Assume  T  —  3. 

2.  Compute  the  heat  loss  per  hour,  per  square  foot  of  area,  of  a  wall 
consisting  of  two  thicknesses  of  1  inch  pine  boards  with  an  air  space  of  2 
inches  between.     Room  temperature  60°,  outside  temperature  10°.     Assume 
T  =  1.8. 

3.  Compute  the  heat  loss  for  the  wall  in  Prob.  2  assuming  a  single  wall, 
2  inches  thick.     What  percentage  of  the  heat  loss  is  saved  by  the  air  space 
when  the  two  1  inch  thicknesses  are  used. 

4.  Compute  the  heat  loss  per  hour,  per  square  foot  of  area,  of  a  wall 
consisting  of  1  inch  oak  boards,  an  air  space  of  1  inch,  and  4  inches  of 
brickwork. 

5.  In  the  room  of  Fig.  7  (Example  1)  find  the  percentage  of  the  heat  loss 
which  would  be  saved  during  a  heating  season  of  8  months  if  double  windows 
were  used.     Assume  average  temperature  of  the  room  and  the  surrounding 
rooms  to  be  65°  and  the  average  outside  temperature  to  be  40°. 

6.  Taking  the  same  room  as  in  Example  1,  heated  to  a  temperature  of  60°, 
with  the  surrounding  rooms  at  70°  and  the  air  outside  at  10°,  how  much 
heat  must  be  supplied  to  the  room  per  hour?     Inside  walls  are  of  lath  and 
plaster.     Ceiling  is  6f  lath  and  plaster,  with  single  floor  above,  and  the  room 
below  has  its  ceiling  plastered. 

7.  Take  the  same  room  as  Example  1,  except  that  the  room  is  covered 
by  a  flat  tin  roof.     The  air  space  between  the  ceiling  of  the  room  and  roof 
should  be  assumed  to  'be  at  a  temperature  of  32°. 


CHAPTER  III 
DIFFERENT  METHODS  OF  HEATING 

20.  Direct  and  Indirect  Heating  Systems. — We  have  seen  that 
to  maintain  the  rooms  of  a  building  at  a  comfortable  temperature, 
it  is  necessary  to  supply  continuously  a  definite  amount  of  heat 
to  each  room,  equal  to  the  amount  lost  from  the  room.     It  is  the 
function  of  the  heating  system,  taken  as  a  whole,  to  extract  the 
heat  from  the  fuel  (by  combustion)  and  deliver  to  the  rooms 
where  it  is  needed.     In  many  kinds  of  buildings,  particularly 
where  large  numbers  of  people  congregate  or  where  fumes  or 
odors  are  given  off  by  industrial  processes,  making  artificial 
ventilation  necessary,  the  warming  of  the  supply  of  air  required 
for  ventilation  is,  part  of  the  task  of  the  heating  system.     So 
closely  are  the  problems  of  heating  and  ventilating  related  that  it 
is  imperative  that  they  be.  considered  together. 

The  heat  supplied  to  the  various  rooms  may  be  delivered  there 
as  radiant  heat  only,  $s  is  practically  the  cas$  with  a  grate  fire  or 
by  convection  onhr  as  in  the  cas*e  of  a  hot  air  furnace,  or  by  a 
combination  of  the  two  methods,  as  in  the  case  of  a  steam  radiator. 
In  general,  a  heating  system  which  heats  principally  or  wholly  by 
convection  is  more  satisfactory  than  one  which  delivers  its  heat 
entirely  by  radiation;  the  room  heated  by  convection  is  usually 
much  more  uniformly  and  comfortably  heated. 

Heating  systems  may  be  roughly  divided  into  two  classes, 
depending  on  the  location  of  the  sources  of  heat.  When  the 
source  of  heat,  such  as  a  radiator,  stove  or  grate  is  located  in  the 
room  to  be  heated,  this  is  known  as  direct  heating.  In  indirect 
systems  the  source  of  heat  is  located  outside  of  the  room  and  the 
heat  is  conveyed  to  the  room  by  a  current  of  air.  Under  the 
head  of  indirect  systems  come  hot  air  furnaces  and  the  various 
types  of  fan  systems.  Before  studying  the  design  of  the  various 
systems  of  heating,  it  is  desirable  to  understand  in  general  their 
advantages  and  disadvantages. 

21.  Grates. — The  most  primitive  form  of  heating  apparatuses 
the  grate.    .In  the  grate  the  air  which  passes  through  the  fire,  and 
is  heated  by  the  fire,  all  passes  up  the  chimney  and  only  the  heat 
given  off  by  radiation  to  the  walls  and  objects  in  the  room  and 

25 


26  HEATING  AND  VENTILATION 

the  small  amount  given  off  by  the  chimney  walls  is  effective  in 
heating  the  room.  In  grates  of  better  construction  this  condition 
is  somewhat  improved  by  surrounding  the  grate  with  firebrick  so 
arranged  that  it  becomes  highly  heated  and  radiates  heat  to  the 
room.  But  the  fact  that  all  the  air  heated  by  the  grate  passes  up 
the  chimney  makes  the  grate  a  very  uneconomical  form  of  heat- 
ing. In  the  best  forms  of  open  grates  only  about  20  per  cent,  of 
the  heat  of  the  fuel  is  effective  in  heating  the  room.  This 
form  of  heating,  however,  is  highly  recommended  by  many  and 
is  a  very  popular  method  of  heating  throughout'  England  and 
Scotland.  The  feeling  of  a  grate-heated  room  is  quite  different 
from  that  of  a  room  heated  by  other  means.  All  of  the  heat  is 
given  off  by  radiation  and  the  air  is  at  a  considerably  lower 
temperature  than  the  objects  in  the  room,  owing  to  the  fact 
that  the  radiated  heat  does  not  heat  the  air  through  which  it 
passes.  The  air  of  the  room  being  at  a  much  lower  teniperature, 
its  capacity  for  moisture  is  not  increased  as  much  as  it  would  be 
were  the  air  heated  to  a  higher  temperature.  The  result  is 
that  the  air  contains  proportionately  more  moisture  than  is  the 
case  with  most  other  forms  of  heating,  which,  no  doubt,  is  an 
advantage.  Also,  the  undeniably  cheerful  aspect  of  an  open 
fire  is  in  its  favor. 

On  the  other  hand,  it  is  impossible  to  heat  the  room  uniformly 
and  a  person  is  either  hot  or  cold,  depending  on  his  distance  from 
the  fire.  The  labor,  dust,  and  dirt  attendant  upon  the  main- 
tenance of  grate  fires  is  another  disadvantage.  Heating  by  means 
of  grates  is  practiced  only  in  the  more  moderate  climates.  Grates 
are  useful  in  houses  heated  by  other  means,  as  the  open  chimney 
forms  a  most  efficient  foul-air  flue  and  greatly  improves  the 
ventilation. 

22.  Stoves. — The  stove  is  a  marked  improvement  over  the 
grate,  particularly  from  the  standpoint  of  economy.  The  modern 
base-burner  stove  is  one  of  the  most  efficient  forms  of  heating 
apparatus,  making  use  of  from  70  to  80  per  cent,  of  the  heat  in  the 
fuel.  In  heating  a  room,  the  hot  surface  of  the  stove,  being  at  a 
higher  temperature  than  that  of  the  surrounding  objects  in  the 
room,  radiates  heat  directly  to  those  objects.  In  addition,  heat 
is  given  to  the  air  of  the  room  by  contact  with  the  hot  surface  of 
the  stove.  In  selecting  a  stove  to  heat  a  given  room  care  should 
be  taken  to  choose  one  of  ample  size  so  that  only  in  the  coldest 
weather  would  it  be  necessary  to  keep  the  drafts  wide  open  in 


DIFFERENT  METHODS  OF  HEATING  27 

order  to  heat  the  room.  At  the  present  time  the  stove  as  a  general 
source  of  heat  is  being  rapidly  discarded  because  of  the  attendance 
required,  the  space  occupied,  the  unsightly  appearance  of  the 
stove,  and  the  fact  that  a  separate  stove  is  required  in  every  room 
for  satisfactory  results. 

23.  Hot-air  Furnaces. — The  hot-air  furnace  is  the  natural 
outgrowth  of  the  stove.  In  this  system  one  large  furnace  is 
placed  in  the  basement  of  the  building,  and  the  air  is  taken 
from  the  outside  or  recirculated  from  the  house,  passed  over  the 
surfaces  of  the  furnace,  and  carried  up  through  the  flues  to  the 
rooms  to  be  heated.  In  the  simplest  type,  the  so-called  pipeless 
furnace,  the  heated  air  is  delivered  only  to  the  room  directly  over 
the  furnace,  and  passes  into  the  other  rooms  through  the  open 
doorways  by  natural  circulation  only.  For  any  but  the  smallest 
houses,  however,  a  f urnape  having  separate  pipes  to  the  individual 
rooms  is  "preferable.  The  principal  fl.Hva,T)tfl,p;ps  of  the  hot-air 
furnace  are  that  it  provides  a  cheap  and  rather  efficient  method  of 
furnishing  both  heat  and  ventilation,  requires  little  attendance, 
and  does  not  deteriorate  rapidly  when  properly  taken  care  of. 
The  greatest  disadvantage  of  this  system  is  fhat  tho^circulation 
of  the  heated  air  depends  entirely  upon  natural  draf^that  is,  it 
depencTslipoiT  the  difference  in  weight  between  the  air  inside  the 
flues  and  the  air  outside  the  flues.  This  difference  is  extremely 
small,  so  that  the  force  prpxju^ing  circulation  in  the  flue  is  not 
large.  When  a  very  strong  wind  blows  against  one  side  of  the 
house,  air  from  the  outside  enters  through  the  window  cracks  and 
other  small  opening  forming  a  slight  pressure  in  the  rooms  and 
preventing  the  >arm  air  from  entering,  thus  making  it  difficult 
to  heat  the  rrjOms  on  that  side  of  the  house.  If  the  system  is 
carefully  d  3Signed,  however,  this  difficulty  can  be  overcome 
in  a  measu  re>  Another  serious  objection  to  the  hot-air  furnace 
is  that  it  j'g  seldom  dust-tight,  and  dust,  ashes,  and  gases  from  the 
fire  are  Carried  into  the  rooms.  In  general,  the  hot-air  furnace 
may  bff.  considered  as  a  very  good  type  of  heating  plant  for 
small  Residences,  but  because  of  the_smalL  force  available  for 
produlrcmg  circulation  its  use  is  limited  to  buildings  where  the 
lengtlj  Of  the  horizontal  flues  does  not  exceed  15  feet. 

In!  the  case  of  the  hot-air  furnace,  the  heat  is  carried  from  the 
furnace  by  the  air  which  passes  around  the  furnace  and  then 
ente/rs  theTobms  through  the  flues.  This  air  circulates  in  the 
roo%  and  heats  the  contents  of  the  room  and  supplies  the  heat 


28  HEATING  AND  VENTILATION 

which  is  lost  through  the  walls.  The  economy  of  the  hot-air 
system  will  vary,  depending  on  the  relative  proportions  of  the 
air  taken  from  the  outside  and  from  the  rooms.  If  the  air  enter- 
ing the  furnace  is  taken  from  the  house  and  not  from  the  outside, 
the  economy  of  the  hot-air  furnace  will  be  about  the  same  as 
that  of  the  steam  system.  If,  however,  cold  air  be  taken  from 
the  outside,  an  additional  amount  of  heat  will  be  used  in  heating 
this  cold  air  up  to  the  temperature  of  the  rooms.  Control  of 
the  heat  supply,  with  a  hot-air  furnace,  is  readily  obtained  by 
adjusting  the  dampers  at  the  registers  in  each  room  and  by 
manipulating  the  furnace  drafts. 

24.  Direct  Steam  Heating. — From  the  standpoint  of  ventila- 
tion, direct  steam  heating,  without  other  means  for  ventilation, 
is  not  as  desirable  as  the  hot-air  furnace.     Mechanically,  how- 
ever, it  has  many  advantages.     The  radiator  is  easily  adapted 
to  almost  any  location  in  the  room  and  its  operation  is«  not 
affected  by  the  winds.     The  circulation  of  the  system  is  positive 
and  a  distant  room  can  be  heated  as  easily  as  those  close  to  the 
boiler. 

In  the  older  forms  of  direct  steam-heating  systems  control 
of  the  heat  supply  is  difficult  because  the  radiators,  being  large 
enough  to  heat  the  room  on  the  coldest  days,  give  off  too  much 
heat  for  average  conditions.  The  construction  of  the  older 
forms  of  this  type  of  system  is  sihnivhat  the  radiator  must  give 
off  its  full  output  of  heat  if  it  is  in  use  ?-t  all.  To  maintain  an 
even  temperature  in  average  weather,  fu^uent  opening  and 
closing  of  the  radiator  valves  is  necessary.  In  recent  years  this 
disadvantage  has  been  overcome  in  the  so-cJled  "vapor" 
systems  which  make  use  of  steam  at  pressures  but  Sightly  higher 
than  atmosphere,  and  in  some  cases  below  atmos1  ^here.  In 
these  systems  the  steam  supply  to  each  radiator  can  be  Controlled 
at  the  inlet  valve  so  that  only  the  quantity  actually  reVluired  is 
admitted  to  the  radiator,  and  much  better  regulation  js  there- 
fore possible  providing  the  proper  attention  is  given  to  tlie  con- 
trol of  the  heat  supply  by  the  occupants  of  the  buildingA 

Automatic  control  of  the  heat  supply  also  eliminates  th  is  tr<Puble 
and  is  often  made  use  of  in  certain  classes  of  buildings.     Thdi 
ciency  of  the  direct  steam-heating  system  in  a  well-designed  pj1 
is  from  50  to  70  per  cent. 

25.  Direct  Heating  by  Hot  Water.— The  application  of  diij'ect 
hot-water  radiators  as  a  method  of  heating  is  similar  to  that ;  of 


DIFFERENT  METHODS  OF  HEATING  29 

steam,  with  the  exception  that  the  surfaces  are  usually  at  a 
much  lower  temperature  and  more  radiating  surface  is  therefore 
required.  Hot-water  systems  are  preferable  to  ordinary  steam 
systems  in  that  the  temperature  of  the  radiating  surfaces  can  be 
easily  controlled,  and  can  be  anywhere  from  the  temperature  of 
the  room  to  190°,  or  even  higher  in  the  case  of  certain  forms  of 
hot-water  systems.  Another  advantage  is  that  the  surface  of  the 
radiator,  being  at  a  lower  temperature,  gives  off  more  heat 
by  convection  and  less  by  radiation,  which  tends  to  keep  the 
room  at  a  more  uniform  temperature  throughout  and  makes 
it  more  comfortable  to  the  occupants. 

•  JEEot-Water  heating  is  considered  especially  suitable  for  hospi- 
tals and  other  public  buildings  where  it  is  desirable  to  control 
the\  supply  of  heat  from  a  central  point.  By  varying  the  tem- 
perature of  the  water  at  the  heating  plant  the  supply  of  heat 
and  the  temperature  of  the  building  can  be  approximately  con- 
trolled according  to  the  outside  temperature.  ^The  principal  dis- 
advantage of  the  hot-water  system  lies  in  the  fact  that  the 
circulation  of  the  system  is  ordinarily  produced  only  by  the 
difference  in  weight  between  the  water  in  the  hot  leg  of  the  system 
and  that  in  the  cold  leg  of  the1  system J  The  difference  in  tem- 
perature between  the  two  legs 'is  small*,  being  usually  about  10° 
to  20°,  so  that  the  resulting  force  producing  circulation  is  there- 
fore small.  It  is  necessary  to  be  very  careful  in  designing  the 
piping  for  a  hot-water  sys'tem  as  the  circulation  may  be  easily 
affected  by  the  friction  in  the  piping  and  the  height  of  the  radia- 
tor above  the  boiler.  The  greater  the  height  above  the  boiler 
the  greater  will  be  the  difference  in  weight  between  the  two  col- 
umns of  water  and  {he  stronger  will  be  the  force  producing  cir- 
culation. This  system  in  general  requires  more  careful  design 
and  construction  than  the  steam  system.  Another  disadvantage 
is  that,  because  of  the  great  thermal  capacity  of  the  water  con- 
tained in  the  system,  considerable  time  is  necessary  to  change 
its  temperature  and  the  system  cannot~"be~ina6!e"  to  respond 
quickly  to  sudden  changes  in  the  demand  for.Jieat.  The  efficiency 
of  the  hot-water  system  is-  practically  the  same  as  that  of  a 
steam  system  and  we  may  expect  to  obtain  in  the  rooms  from 
50  to  70  per  cent,  of  the  heat  in  the  fuel. 

Where  hot-water  heating  is  used  in  large  buildings  the  circula- 
tion is  produced  by  a  pump.  The  difficulty  of  circulation  is  then 
done  away  with  and  the  flow  of  water  is  certain  and  rapid. 


30  HEATING  AND  VENTILATION 

26.  Indirect  Steam  and  Hot -water  Heating  by  Natural  Circu- 
lation.— In    heating   with   indirect    steam    or   water   radiation 
cold  air  is  drawn  from  the  outside,  passed  through  and  around 
the  hot  radiator,  which  is  usually  situated  in  the  basement,  and 
delivered  through  flues  to  the  rooms  to  be  heated.     Frequently 
the  circulation  is  produced  entirely  by  the  difference  in  density 
of  the  cold  and  heated  air,  commonly  termed  natural  or  gravity  -? 
circulation.     The  method  of  introducing  the  air  into  the  rooms  is 
quite  similar  to  that  employed  in  the  hot-air  furnace.     The 
principal  advantages  of  indirect  steam  and  water  heating  over 

the  hot-air  furnace  are  that  each  room  has  a  separate  source  or^ ^ 

heat,  the  system  is  not  affected  by  the  winds,  and  no  dust  or 
obnoxious   gases   are    carried   to   the    rooms.     The   source   of 
heat   being   independent   of   the  position  of  the   boiler,   it  is 
possible    to    place    the    indirect    radiators    anywhere    in    the 
building  and  long  air  flues  are  not  necessary.     This  makes  the 
indirect  radiator  much  more  certain  in  operation  than  the  hot- 
air  furnace. 

The  disadvantages  of  indirect  heating  are  the  increased  cost 
and  complication  of  the  system  and  the  tendency  for  dust  to 
accumulate  in  the  air  flues. 

The  application  of  indirect  hot-water  radiators  is  similar  to 
that  of  steam  radiators  and  the  economy  is  practically  the  same, 
although  the  use  of  hot  water  for  indirect  heating  has  been  much 
more  limited  than  the  use  of  steam.  The  installation  of  indirect 
hot-water  radiators  must  be  done  with  great  care  so  that  each 
radiator  will  at  all  times  have  the  proper  amount  of  water  circu- 
lating through  it,  for  if  for  any  reason  the  circulation  is  stopped 
the  water  in  the  radiator  will  be  in  danger  of  freezing.  In  mild 
climates  this  difficulty  would  not  be  as  serious  as  in  locations 
where  the  weather  is  extremely  cold. 

27.  Fan  Systems  of  Heating. — In  buildings  of  a  public  or 
semi-public   character,   where   a  large   number   of   people   are 
gathered  in  a  relatively  small  space,  it  is  necessary  to  provide 
adequate  ventilation.     With  the  systems  that  have  been  pre- 
viously described  it  is  impossible  to  introduce  sufficient  quanti- 
ties of  air  to  ventilate  such  buildings  properly.     It  may  be  said 
in  general  that  no  system  of  natural  circulation  has  ever  produced 
satisfactory  ventilation  in  a  room  occupied  by  a  large  number  of 
people;  it  is  necessary  to  provide  some  mechanical  means  for 
creating    a    positive    circulation    which    is    not    affected    by 


DIFFERENT  METHODS  OF  HEATING  31 

winds  or  by  the  distance  of  the  room  from  the  source  of  heat. 
In  a  system  of  mechanical  ventilation  the  air  is  taken  from 
the  outside,  or  sometimes  recirculated  from  the  inside,  and  is 
passed  through  the  heating  coils  and  forced  .into  the  building 
by  a  fan. 

There  are  four  general  methods  of  heating  and  ventilating 
with  a  fan  system.  Jii^he  first  method,  the  heat  losses  through 
the  walls  and  windows  are  taken  care  of  by  direct  radiation 
installed  in  the  various  rooms  in  the  ordinary  way.  TheJ:an 
s_J^^  ventilation, 


warmed  to  a  temperature  of  approximately  70°. 

In  the  second  method,  no  direct  radiation  is  installed  and  the 
heating  and  ventilating  are  done  entirely  by  the  fan  syst'eni. 
This  means  that  the  air  must  "be  introduced  at  a  temperature 
considerably  above  the  room  temperature.  The  fan  system  is 
so  arranged  that  a  part  of  the  incoming  air  is  rather  highly  heated 
and  passes  into  a  hot  air  chamber,  the  remainder  being  heated 
only  to  about  70°  and  passing  into  the  tempered  air  chamber. 
A  single  duct  goes  to  each  room  of  the  building  and  is  provided 
with  dampers  so  that  part  of  the*  air  can  be  taken  from  the  hot 
air  chamber  and  part  from  the  tempered  air  chamber  in  amounts 
depending  upon  the  quantity  of  heat  required.  These  dampers 
are  usually  controlled  by  an  automatic  device  to  maintain  a 
constant  temperature  in  the  room. 

The  third  method  is  a  combination  of  the  first  and  second. 
A  portion  of  the  heat  losses  through  the  walls  and  windows 
(usually  one  third),  as  well  as  the  ventilation  requirements,  is 
supplied  by  the  fan  system.  The  balance  of  the  heat  loss  through 
the  walls  and  windows  is  supplied  by  direct  radiation. 

In  the  fourth  method  the  fan  system  is  used  for  heating  only 
and  there  is  no  direct  radiation.  Warm  air  is  discharged  by  the 
fan  through  ducts  to  the  heated  room*,  and  is  thence  returned  to 
the  heater  and  fan.  This  method  is  used  principally  in  factory 
buildings. 

28.  Combinations  of  Different  Systems.  —  In  addition  to  the 
combinations  just  described,  of  direct  radiation  and  fan  ventila- 
tion, there  have  been  deviseol  innumerable  combinations  —  com- 
binations of  direct  and  indirect  steam  systems,  direct  and 
indirect  hot  water,  water  and  hot  air,  and  steam  and  hot  air. 
The  combinations  which  have  been  most  us§d  are  those  of  direct- 
and  indirect  steam  systems  and  of  hot  waterltrith  hot  air. 


32 


HEATING  AND  VENTILATION 


29.  Classification  of  Heating  Systems- 


Grate 
Stove 

Hot  Air  Furnace 


Direct  Radiation 


Pipe 
Pipeless 

Fan  and  Furnace  System 
Combination  with  Hot  Water 
Pressure  System 

Steam    Vapor  System       f  A . 
\r  ci     j.        J  -^-ir 

Vacuum  System  m 

Gravity 
Hot  Water    Pressure 

Forced  Circulation 


Gravity  Indirect  Radiation   J  Total  Indirect 
(Steam  or  Water)  [  Direct-indirect 

Ventilation  by  fan — heating  by  direct  radiation. 
Ventilation  and  part  of  heating  by  fan — balance 

by  direct  radiation. 
Ventilation  and  heating  by  fan. 
Heating  by  fan — no  ventilation. 
Unit  Ventilator  System. 
Fan  and  Furnace  System. 


Fan  Systems 

(Steam  or  Water) 


30.  Economy  of  Heating  Systems. — The  economy  of  any  heat- 
ing system  depends  upon  the  completeness  with  which  the  heat 
in  the  fuel  is  effectively  utilized  in  heating  the  building.  The 
principal  sources  of  loss  and  the  manner  in  which  the  heat  is 
utilized  in  any  type  of  heating  system  are  as  follows: 

Losses: 

Imperfect  combustion. 

Sensible  heat  in  the  chimney  gases. 

Combustible  in  the  ash. 

Radiation  from  boiler  or  furnace. 

Radiation  from  flues  or  piping. 

Losses  through  excessive  temperature  in  the  building. 
Heat  utilized: 

Heat  utilized  in  supplying  the  heat  losses  from  the  building. 

Heat  used  for  ventilation. 

Of  the  losses,  the  first  three  are  dependent  rather  upon  the 
design  of  the  furnace  or  boiler  than  upon  the  type  of  heat- 
ing system.  The  radiation  from  the  boiler  or  furnace  is  partially 
recovered  as  it  serves  to  warm  the  basement  and  decreases  the 
heat  loss  to  the  basement  from  the  rooms  above.  The  loss  from 
this  source  is  fairly  constant,  regardless  of  the  amount  of  heat 


DIFFERENT  METHODS  OF  HEATING  33 

delivered  by  the  boiler  or  furnace  and  if  a  very  low  fire  is  carried, 
as  in  mild  weather,  it  may  become  quite  appreciable  in  compari- 
son with  the  heat  delivered.  The  loss  from  the  flues  or  piping 
is  also  partially  utilized  in  warming  the  building. 

The  heat  used  to  supply  the  heat  losses  from  the  building  is  the 
principal  product  of  any  heating  system.  A  part  of  this  heat 
may  be  considered  as  a  loss,  however,  if  excessive  temperatures 
are  maintained  either  during  the  hours  when  the  building  is 
occupied,  or  during  the  night  or  other  times  when  a  low  tempera- 
ture could  be  carried. 

The  amount  of  heat  used  for  ventilation  will  depend  upon  the 
amount  of  fresh  air  supplied.  The  air  introduced  for  ventilation 
is  discharged  from  the  building  at  room  temperature,  and  the 
heat  contained  in  this  air  in  excess  of  the  heat  in  the  outside  air 
is  evidently  the  amount  chargeable  to  ventilation.  While  this 
item  might,  from  the  standpoint  of  heating  only,  be  considered 
as  a  loss,  it  is  really  the  price  that  must  be  paid  for  good  ventila- 
tion, which  is  essential  to  health  and  comfort.  In  many  States 
there  are  laws  which  specify  the  minimum  amount  of  air  which 
must  be  furnished  per  hour  for  each  occupant  in  theatres  and 
other  buildings  of  a  public  character.  The  necessity  and  impor- 
tance of  ventilation  will  be  discussed  in  later  chapters. 


CHAPTER  IV 
HOT-AIR  FURNACE  HEATING    ^ 

31.  Furnace  Systems. — In  the  hot-air  furnace   system,   the 
heat  is  developed  from  the  fuel  by  combustion  in  the  furnace  and 
is  conveyed  by  currents  of  air  to  the  rooms  to  be  heated.     There 
are  three  general  types  of  hot-air  furnaces. 

In  the  ordinary  furnace  the  pipes  radiate  to  the  various  rooms, 
each  pipe  supplying  one  or  sometimes  two  rooms.  The  air  is 
sometimes  re-circulated  through  the  furnace  and  re-heated,  but 
in  many  cases  fresh  air  is  drawn  in  from  outside  continuously. 

In  the  pipeless  furnace,  as  the  name  indicates,  no  pipes  are  run 
to  the  rooms.  The  heated  air  is  delivered  to  the  room  directly 
above  the  furnace. 

The  third  type  of  furnace  system  is  the  forced  circulation 
system,  sometimes  employed  in  certain  types  of  buildings.  A 
positive  circulation  is  maintained  in  this  system  by  a  fan,  making 
the  operation  of  the  system  much  more  certain  than  in  the  ordi- 
nary arrangement. 

32.  General  Arrangement. — Figure  8  shows  the  general  ar- 
rangement of  an  ordinary  pipe  furnace  system.     The  hot  air 
pipes  radiate  from  the  upper  part  of  the  furnace  casing  to  the 
various  rooms.     The  cold  air  enters  at  the  bottom  of  the  furnace. 
It  may  be  taken  entirely  from  outside  or  re-circulated  entirely 
from  inside,  or  taken  partly  from  each  source,  depending  upon 
the  amount  of  fresh  air  that  is  desired  for  ventilation.     If  taken 
from  the  outside,  more  fuel  is  required,  as  the  cold  air  must  be 
heated  through  a  greater  range  of  temperature.     For  the  ordinary 
residence  it  is  usually  unnecessary  to  take  much,  if  any,  fresh 
air,  for  the  normal  leakage  of  air  into  and  out  of  the  building 
is  sufficient  for  most  conditions  of  occupancy. 

It  is  essential  to  the  proper  operation  of  the  furnace  system 
that  the  air  in  the  rooms  be  continuously  replaced  by  heated  air 
from  the  furnace.  In  a  re-circulating  system,  the  cooling  air  in  the 
rooms  falls  to  the  floor  and  finds  its  way  through  the  doorways 
and  down  the  stairs  to  the  re-circulating  register.  When  fresh 

34 


HOT-AIR  FURNACE  HEATING 


35 


air  is  used,  it  necessarily  displaces  an  equal  amount  of  air  from  the 
rooms  which  must  find  its  way  out  of  the  building  through  cracks 
around  the  windows,  doors,  etc.  Foul  air  flues  leading  up  to  the 
roof  are  sometimes  provided- for  the  purpose. 


FIG.  8. — General  arrangement  of  furnace  system. 

33.  Furnaces. — The  hot-air  furnace  consists  fundamentally 
of  a  firepot  and  a  series  of  passages  for  the  flue  gases,  surrounded 
by  a  metal  or  brick  casing.  The  air  circulates  through  the  space 
between  the  furnace  proper  and  the  casing,  absorbing  heat  from 
the  hot  surfaces  of  the  firepot  and  gas  passages.  The  gas  pas- 
sages are  usually  formed  by  a  simple  casting  called  a  " radiator." 

Hot-air  furnaces  are  quite  varied  in  design.  In  general  there 
are  two  types :  those  with  the  radiator  at  the  top  of  the  furnace, 
as  in  Fig.  9,  and  those  with  the  radiator  near  the  bottom  of 
the  furnace,  as  in  Fig.  10.  Occasionally,  in  cheap  furnaces, 
the  radiator  is  left  off  entirely.  For  the  best  possible  efficiency 
in  any  furnace  the  entering  air  should  first  come  into  contact 
with  the  surfaces  behind  which  are  the  coldest  flue  gases  and  the 
air  leaving  the  furnace  should  pass  over  the  hottest  surfaces. 
This  ideal  condition  is  difficult  of  realization,  for  mechanical 
reasons,  but  the  furnace  which  most  nearly  approaches  it  will 
in  general  be  the  most  efficient. 

The  heating  surfaces  of  a  furnace  may  be  divided  into  two 
classes:  (a)  direct  heating  surfaces,  which  are  those  which  are 
in  contact  with  the  fire  or  which  receive  heat  by  direct  radiation 


36 


HEATING  AND  VENTILATION 

Eadiator 


FIG.  9. — Furnace  with  radiator  at  the  top  (casing  removed) 


FIG.  10. — Furnace  with  radiator  near  bottom  (casing  removed). 


HOT-AIR  FURNACE  HEATING  37 

from  the  fire;  and  (6)  indirect  heating  surfaces,  which  are  heated 
only  by  the  hot  gases.  In  addition  there  are  some  surfaces 
which  deliver  heat  only  by  conduction  to  the  heating  surfaces 
proper,  such  as  projections  and  braces,  these  being  called  ' 'ex- 
tended" surfaces.  The  parts  of  such  surfaces  which  are  more 
than  about  2  inches  from  actual  heating  surface  are  of  doubtful 
effectiveness,  however. 

All  of  the  heating  surfaces  give  up  heat  to  the  air  entirely  by 
convection.  The  amount  of  heat  transmitted  through  the  heat- 
ing surfaces  of  course  increases  as  the  difference  in  temperature 
between  the  air  and  the  products  of  combustion  increases.  The 
effectiveness  of  the  heating  surfaces  decreases  as  the  distance 
from  the  fire  increases.  Direct  heating  surfaces  are  naturally 
more  effective  than  indirect  heating  surfaces.  The  more  rapid 
the  flow  of  air  over  the  heating  surfaces,  the  greater  will  be  the 
amount  of  heat  removed  from  them: 

Since  the  effectiveness  of  the  heating  surfaces  depends  upon 
the  design  of  the  furnace,  it  is  impossible  to  base  the  capacity 
of  the  furnace  upon  the  amount  of  heating  surface.  Roughly, 
however,  the  heat  transmission  may  be  assumed  to  be,  on  an 
average,  from  1000  to  1500  B.t.u.  per  hour  per  square  foot  of 
surface. 

34.  Furnace  Construction. — The  firepot  and  radiator  are 
usually  made  of  cast  iron,  although  steel  is  sometimes  used. 
There  is  no  appreciable  difference  in  the  thermal  conductivity 
of  the  two  materials.  It  is  essential  that  the  joints  between  the 
different  castings  be  air-tight  so  that  the  products  of  combustion 
cannot  escape  and  be  carried  to  the  rooms  above.  The  joints, 
therefore,  are  of  a  modified  tongue  and  groove  design,  the  grooves 
being  filled  with  a  cement  and  the  castings  drawn  and  held 
together  with  draw  bolts.  Joints  should  be  as  few  as  possible 
and  vertical  joints  should  be  avoided. 

The  firepot  is  usually  slightly  conical  and  should  be  deep 
enough  to  contain  sufficient  coal  to  last  for  8  hours,  leaving 
enough  unburned  coal  on  the  grates  at  the  end  of  that  time  to 
ignite  the  fresh  charge  of  fuel.  With  hard  coal  this  means  that 
the  depth  should  be  sufficient  to  allow  for  50  pounds  of  coal 
being  placed  on  the  grate  per  square  foot  of  grate.  Coke  or 
soft  coal  will  require  a  greater  depth  of  firebox  than  anthracite 
coal.  The  grate  area  is  usually  from  1:25  to  1:12  of  the  area 
of  the  heating  surface,  the  proportion  depending  upon  the  kind 


38  HEATING  AND  VENTILATION 

of  fuel  and  the  size  of  the  furnace — the  larger  the  furnace,  the 
smaller  the  ratio.  For  anthracite  coal  the  ratio  seldom  exceeds 
1 : 25.  For  bituminous  coal  it  is  usually  1 :  20  and  for  coke  1 : 15 
for  furnaces  of  average  size.  Some  furnaces  have  a  much  greater 
proportion  of  heating  surface  and  are  more  efficient,  although 
their  first  cost  is  greater. 

For  burning  soft  coal  some  furnaces  are  provided  with  an 
auxiliary  air  supply  so  arranged  that  heated  air  is  introduced 
into  the  firepot  above  the  fuel  bed,  mixing  with  the  combustible 
gases  and  promoting  complete  and  smokeless  combustion. 

The  furnace  casing  is  usually  of  galvanized  iron,  although 
large  furnaces  are  sometimes  enclosed  by  brickwork.  When  a 
galvanized-iron  casing  is  used,  insulation  is  obtained  by  providing 
an  inner  casing  of  black  iron  or  tin  with  an  air  space  between 
the  inner  casing  and  the  outer  casing  of  about  1  inch.  The 
area  between  the  furnace  and  casing  should  be  sufficient  so  that 
no  appreciable  resistance  is  interposed  to  the  circulation  of  air 
through  the  furnace.  In  small  furnaces  the  velocity  should  not 
exceed  250  feet  per  minute  and  in  larger  furnaces  300  to  350  feet 
per  minute.  These  figures  apply  only  to  gravity  circulation. 

The  capacity  of  a  hot  air  furnace  depends  primarily  upon 
the  size  of  the  firepot.  To  supply  the  heat  required  for  any 
given  building,  a  certain  amount  of  fuel  must  be  burned  per 
hour.  The  firepot  must  be  of  sufficient  size  to  hold  the  fuel 
required  for  a  period  of  at  least  eight  hours.  Under  ordinary 
conditions,  from  4  to  7  pounds  of  coal  can  be  consumed  efficiently 
per  square  foot  of  grate  per  hour.  The  heat  developed  per  pound 
of  fuel  consumed  and  the  efficiency  of  its  utilization  must  also 
be  taken  into  account  in  determining  the  furnace  capacity  re- 
quired for  a  given  case. 

Suppose,  for  example,  that  a  house  requires  in  zero  weather 
175,000  B.t.u.  per  hour.  Assume  that  the  furnace  efficiency 
is  70  per  cent,  and  that  the  coal  contains  12,300  B.t.u.  per  pound. 
Assuming  a  combustion  rate  of  6  pounds  per  square  foot  of  grate 
area  per  hour,  the  grate  area  required  would  be  175,000  -r-  (12,300 
X  0.70  X  6)  =  3.38  sq.  ft. 

Furnaces  are  rated  by  the  manufacturers  either  upon  a  basis 
of  the  volume  of  the  building  to  be  heated  or  upon  the  total 
cross-sectional  area  of  the  warm  air  ducts.  Inasmuch  as  these 
ratings  usually  represent  about  the  maximum  capacity  of  the 
furnace,  it  is  well  to  check  each  case  by  the  method  given  above. 


HOT-AIR  FURNACE  HEATING  39 

35.  Humidification. — When  the  cold  outdoor  air  is  heated 
to  room  temperature  its  relative  humidity  decreases  and  its 
capacity  for  absorbing  moisture  increases  greatly.  The  effect  of 
this  dry  air  on  the  human  system  is  harmful  as  will  be  brought 
out  later  (Chapter  XIII).  Artificial  humidification  is  therefore 
very  desirable. 

The  hot-air  furnace  system  affords  a  particularly  favorable 
opportunity  for  humidification,  but  unfortunately  few  furnaces 
are  equipped  with  adequate  apparatus  for  adding  the  necessary 
amounts  of  moisture  to  the  air.  Most  furnaces  have  some  sort 
of  a  "water  pan"  which  is  usually  installed  near  the  bottom  of 
the  furnace.  This  location  is  entirely  wrong,  for  the  air  as  it 
enters  at  the  bottom  of  the  furnace  has  the  least  capacity  for 
absorbing  moisture.  To  be  effective,  the  humidifying  apparatus 

Evaporating 
/    Pan 


FIG.   11.— Humidifier. 

should  be  placed  where  the  hottest  air  will  pass  over  it,  i.e.,  at 
the  furnace  outlet.  Few  realize  that  in  order  to  maintain  a 
proper  humidity  in  even  a  small  house  there  must  be  evaporated 
hourly  a  quantity  of  water  of  the  order  of  lO^owids.  To  be 
satisfactory,  the  water  pan  must  therefore  be  kept  filled 
automatically  from  the  water-supply  system.  Fig.  11  shows 
a  humidifier  which  is  located  at  the  top  of  the  furnace  and  is 
automatically  filled.  The  amount  of  water  evaporated  increases 
with  the  amount  of  air  passing  through  the  furnace  and  with 
the  temperature  of  the  air,  making  the  apparatus  to  some  extent 
self-regulating.  Accurate  automatic  regulation  is  impossible, 
however,  without  a  system  of  humidity  control  such  as  will  be 
described  later. 

36.  Cold-air  Pipe. — The  air  supply  to  the  furnace  may  be 
taken  from  outside  or  can  be  re-circulated  from  the  house.  It 
is  also  quite  feasible  to  take  only  a  certain  amount  of  air  from 
outside  and  to  supply  the  remainder  by  re-circulation.  With 
complete  re-circulation  the  advantage  of  ventilation  is  entirely 
lost  but  the  system  is  somewhat  more  economical.  The  cold- 


40  HEATING  AND  VENTILATION 

air  duct  may  be  of  galvanized  iron  or  may  be  constructed  of 
tile  and  placed  beneath  the  basement  floor.  It  should  come  from 
the  side  of  the  house  which  is  subject  to  the  prevailing  winds.  It 
is  sometimes  desirable  to  have  cold-air  ducts  leading  to  different 
sides  of  the  house  so  that  the  supply  of  cold  air  may  be  taken 
from  the  windiest  side.  The  cross-section  of  the  cold-air  duct 
should  be  80  per  cent,  of  the  aggregate  area  of  the  supply  ducts 
leaving  the  furnace. 

The  re-circulating  duct  should  be  brought  from  the  coldest, 
part  of  the  house  and  from  some  room  such  as  a  hall  which 
has  other  rooms  leading  into  it.  The  side  of  the  stairway,  the 
lower  stairway  risers,  or  the  space  in  front  of  large  windows  are 
good  locations  for  the  re-circulating  register.  It  is  sometimes 
advantageous  to  install  additional  re-circulating  pipes  to  rooms 
which  are  unfavorably  situated. 

If  it  is  desired  to  re-circulate  partially  and  to  take  the  balance 
of  the  air  from  outside,  the  re-circulating  pipe  should  be  brought 
to  the  furnace  independently  of  the  fresh-air  pipe,  and  a  deflect- 
ing plate  placed  in  the  air  space  under  the  furnace.  If  this 
is  not  done,  the  air  may  come  in  from  the  outside  and  pass  up 
the  re-circulating  pipe  instead  of  through  the  furnace.  Both 
the  fresh-air  pipe  and  the  re-circulating  pipe  must  be  provided 
with  dampers. 

It  is  a  common  error  to  make  the  re-circulating  pipe  of  a 
furnace  system  too  small.  The  area  of  the  re-circulating  pipe 
should  be  not  less  than  three-fourths  the  combined  area  gf  the 
hot-air  pipes,  and  it  is  better  to  have  it  equal  to  their  combined 
area. 

37.  Hot-air  Pipes. — The  furnace  should  be  centrally  located, 
or  if  the  coldest  winds  come  from  a  certain  direction,  it  can  be 
located  toward  that  side  of  the  house  as  the  rooms  nearest  the 
furnace  usually  tend  to  be  the  best  heated.  The  pipes  leading 
from  the  furnace  should  be  as  short  and  direct  as  possible;  long 
horizontal  pipes  should  be  avoided. 

The  horizontal  pipes  are  called  leaders;  the  vertical  pipes 
flues  or  risers.  Leaders  are  usually  made  of  round  pipe.  All 
leaders  should  be  given  the  same  pitch  of  at  least  1  inch  per  foot 
and  should  leave  the  furnace  at  the  same  elevation.  They  should 
be  insulated  with  asbestos  paper,  or  if  extending  through  a  very 
cold  part  of  the  basement,  with  an  air-cell  covering.  It  is  desir- 
able to  provide  a  damper  in  each  pipe  so  that  the  distribution 


HOT-AIR  FURNACE  HEATING 


41 


of  the  air  among  the  different  rooms  can  be  adjusted.  The 
risers  should  in  every  case  be  installed  in  an  inside  partition, 
as  the  cooling  effect,  when  placed  in  an  outside  wall,  would 
greatly  retard  circulation,  besides  causing  an  excessive  waste  of 
heat.  It  is  usually  necessary  to  limit  the  depth  of  .the  riser  to 
4  inches,  so  that  it  may  be  enclosed  in  the  studding.  The  width 
also  is  sometimes  limited  by  the  distance  between  the  studding, 


FIG.  12. — Boot  of  improper 
design. 


FIG.  13. — Boots  of  good  design. 


so  that  it  is  often  difficult  to  install  risers  of  sufficient  area. 
Many  furnace  systems  suffer  from  this  source.  It  is  some- 
times necessary  to  run  two  risers  to  large  second-floor  rooms 
when  space  is  not  available  for  a  single  riser  of  sufficient  size. 
Architects  often  fail  to  realize  the  importance  of  providing  suffi- 
cient space  for  this  purpose. 


FIG.  14. — Floor  register. 


FIG.  15. — Wall  register. 


Risers,  when  made  of  single-walled  pipe  must  be  insulated  with 
asbestos  paper  to  protect  the  woodwork  and  a  clearance  on  all 
sides  of  at  least  Y±  inch  must  be  left.  Double-walled  pipe 
which  has  an  air  space  between  the  walls  is  becohfcg  widely  used.. 
The  air  space  serves  as  an  insulator  and  greatflfeecreases  any 
possible  fire  hazard  as  well  as  reducing  heat  lo«ton  the  pipe. 
When  double-walled  pipe  is  used  the  proper  sij^MPft  be  selected 
so  that  the  net  inside  area  will  not  be  W  Reed  below  the 


42 


HEATING  AND  VENTILATION 


computed  requirements.  Bright  tin  is  ordinarily  used  for  all 
piping. 

The  leader  is  connected  to  the  riser  by  means  of  a  fitting 
called  a  "boot"  shown  in  Figs.  12  and  13.  The  forms  shown 
in  Fig.  13  are  preferable  because  less  resistance  is  interposed  to 
the  flow  of  air. 

The  air  is  delivered  into  the  room  through  registers  of  the 
forms  shown  in  Figs.  14  and  15.  FJoox  registers  have  the  advan- 
tage that  they  may  be  made  of  any  size  and  may  be  placed  in 
any  part  of  the  room.  They  are  often  favored  because  the  air 
leaving  them  does  not  deposit  dust  on  the  walls  as  does  the  side- 
wall  register.  Floor  registers,  however,  are  very  unsanitary  as 


FIG.  16. — Method  of  connecting 
first  floor  register  and  riser  to  a 
single  leader. 


FIG.  17. — Box  for  floor  register. 


they  collect  great  quantities  of  dirt;  and  they  also  frequently 
necessitate  cutting  the  carpets  or  rugs.  On  the  whole,  the  side- 
wall  register  is  much  to  be  preferred.  Registers  are  provided 
with  means  of  cutting  off  the  flow  of  air  in  the  form^of  louvres  or, 
in  the  side-wall  type,  a  single  shutter  of  sheet  metal.  The 
shutters  in  some  of  the  registers  should  be  omitted,  so  that  by  no 
possible  chance  could  all  of  the  air  supply  be  cut  off;  for  with  no 
air  circulating  through  the  furnace,  the  danger  of  overheating 
and  burning  out  the  firepot  is  great. 

It  is  often  convenient  to  supply  a  first-floor  register  and  a 
riser  from  a  single  leader.  This  can  be  satisfactorily  accom- 
plished by  means  of  the  arrangement  shown  in  Fig.  16.  The  free 
area  of  an  ordinary  register  is  only  about  half  of  its  gross  area 
and  its  size  muAtherefore  be  about  double  that  of  the  pipe  which 


HOT-AIR  FURNACE  HEATING 


43 


supplies  it.  For  a  floor  register  a  box  of  the  form  shown  in 
Fig.  17  is  provided  and  for  a  wall  register  a  frame  of  the  form 
shown  in  Fig.  18  is  used. 


FIG.  18. — Stack  and  register  frame — double  walled  pipe. 

38.  Size  of  Hot-air  Pipes. — There  are  two  methods  of  figuring 
the  size  of  the  hot-air  pipes,  the .B.t.u.  method  and  the  vol- 
ume method.  The  former  is  the  more  rational  and  is  the  one 
recommended. 

Example  of  B.t.u.  Method. — Assume  that  the  heat  loss  from 
a  second  floor  room  is  12,000  B.t.u.  per  hour  and  that  the  air 
enters  at  140°,  room  temperature  being  70°.  Each  cubic  foot  of 
air  entering  the  ro®m  will  give  up  enough  heat  to  lower  its  tem- 
perature from  140°  to  70°.  The  amount  of  heat  given  up  when  a 
cubic  foot  of  air  is  cooled  1°  is  approximately  ^5  B.t.u.  There- 
fore the  heat  given  up  per  cubic  foot  is  — ^ —  =  1.27  B.t.u. 

The  volume  of  air  required  per  hour  =  12,000  ^  1.27  =  9460 
cubic  feet.     Allowing  a  velocity  of  4  feet  per  second  in  the  leader, 

the  required  area  of  the  leader  is  4  XT^O^QQ  =  0-66  square  feet. 


. 


a- 


44 


HEATING  AND  VENTILATION 


With  a  velocity  of  400  feet  per  minute  in  the  riser  the  area 
required  would  be  0.39  square  feet. 

The  velocity  of  air  for  first-floor  leaders  may  be  taken  as  3 
to  4  feet  per  second,  for  second-floor  leaders  4  to  5  feet  per  second, 
and  for  third-floor  leaders  5  to  6  feet  per  second.  The  risers 
leading  to  second-  and  third-floor  rooms  may  have  a  velocity  as 
high  as  400  feet  per  minute. 

Registers  should  be  proportioned  so  as  to  give  a  velocity  of 
2  to  3  feet  per  second  on  the  first  floor  and  3  to  4  feet  per  second  on 
the  floors  above,  on  the  basis  of  the  effective  area  of  the  register. 

Volume  Method. — In  the  volume  method  the  area  of  the  hot- 
air  pipe  is  assumed  to  be  purely  a  function  of  the  size  of  the  room, 


8      9     10    11   12    13    14    15    16    17    18    19    20    21   22    23    24    25    26   27   28    29 

Length  of  Room  in  Feet 

Based  on  Ceiling  Height  of  9  Feet 

FIG.  19. — Size  of  hot  air  pipes  for  rooms  of  various  dimensions. 


no  account  being  taken  of  the  heat  losses.  This  method  is 
manifestly  inaccurate  as  the  amount  of  air  required  depends  of 
course  upon  the  heat  lost  from  the  room.  For  rooms  of  average 
proportions  and  of  ordinary  construction,  the  volume  method  is 
usually  successful,  however,  if  carefully  applied.  The  chart  in 
Fig.  19  gives  the  size  of  leaders  and  risers  required  for  rooms  of 
various  dimensions.  It  is  permissible  to  reduce  the  size  of  the 
leader  to  which  a  riser  is  connected,  as  .indicated  by  the  chart, 
because  of  the  acceleration  of  the  circulation  due  to  the  stack 
effect  of  the  riser. 

39.  Suggestions    for    Hot-air    Piping. — The    following    rules 
should  be  observed  in  the  installation  of  the  leaders  and  risers. 


HOT-AIR  FURNACE  HEATING 


45 


Never  use  smaller  than  8-inch  pipe  for  the  leaders. 

When  a  leader  is  more  than  15  feet  long,  add  1  inch  to  the 
diameter  for  each  4  feet  or  fraction  thereof  over  15  feet  and 
increase  the  riser  to  correspond. 

Rooms  on  the  sides  of  the  house  exposed  to  prevailing  winds 
should  have  one  size  larger  pipe  than  rooms  of  equal  size  on  the 
other  sides  of  the  house.  If  the  exposed  rooms  have  a  consider- 
able amount  of  glass  surface,  they  should  have  pipes  two  sizes 
larger. 

Avoid  horizontal  pipes  under  the  second  floor  if  possible. 
When  unavoidable,  make  them  one-fourth  larger  than  the  risers 
and  give  them  all  the  pitch  possible,  avoiding  square  angles. 

In  Table  X  are  given  the  equivalent  areas  of  round  pipes, 
rectangular  pipes,  and  registers. 

TABLE  X. — EQUIVALENT  SIZES  OF  PIPES  AND  REGISTERS1 


Diameter 
of  round 
pipe 

Area  of  pipe, 
square  inches 

Size  flat  riser 
pipe 

Size  side-wall 
register 

Size  round 
floor  register 

Size  rect. 
floor  register 

8 

50 

3^X14 

8X12 

12 

8X12 

9 

64 

4X16 

10X12 

14 

10X12 

10 

78 

4X20 

12X12 

14 

10X16 

11 

95 

6X16 

12X15 

16 

12X15 

12 

113 

6X19 

14X15 

18 

12X20 

13 

132 

6X22 

14X18 

18 

14X18 

14 

154 

8X19 

16X18 

20 

14X22 

15 

176 

8X22 

16X20 

24 

16X20 

16 

201 

8X25 

18X20 

24 

16X24 

17 

227 

10X23 

18X24 

24 

18X24 

18 

254 

10X26 

20X24 

24 

18X27 

19 

283 

12X24 

20X26 

28 

20X26 

20 

314 

12X26 

22X26 

28 

20X30 

21 

346 

12X29 

24X27 

30 

22X30 

22 

380 

14X27 

24X30 

30 

24X30 

23 

415 

14X30 

27X27 

30 

24X32 

24 

452 

14X32 

28X28 

36 

24X36 

All  measurements   in  inches. 

The  circulation  to  a  room  which  is  unfavorably  situated  or 
which  has  a  considerable  amount  of  glass  surface  may  be  aided 
by  installing  a  re-circulating  duct  from  a  register  located  beneath 
the  windows  to  the  lower  part  of  the  furnace  casing. 

1From  "Handbook  of  National  Warm  Air  Heating  and  Ventilating 
Association." 


46  HEATING  AND  VENTILATION 

40.  Foul-air  Flues. — It  is  important  that  n^eans  be  provided 
for  allowing  the  escape  of  air  from  the  various  rooms;  for  fresh 
warm  air  cannot  enter  unless  it  can  displace  an  equal  volume 
ofjroom  air.  The  cracks  around  the  windows  and  doors  usually 
serve  to  allow  air  to  escape,  but  when  located  on  the  exposed 
side  of  the  house,  the  pressure  of  the  wind  prevents  the  outflow 
of  air  and  the  air  supply  to  the  room  may  be  greatly  retarded. 
For  such  rooms  it  is  well  to  provide  either  a  re-circulating  duct 
or  a  foul-air  flue. 

A  fireplace  is  a  very  good  form  of  foul-air  flue.  Foul-air 
flues  if  installed  should  be  enclosed  in  the  inside  partitions 
and  the  registers  should  be  placed  at  the  baseboard.  The  reason 
for  such  an  arrangement  is  that  the  hot  air  entering  the  room 
near  an  inside  partition  rises  to  the  ceiling  and  passes  along 
the  ceiling  to  the  windows  where  it  is  cooled,  dropping  to  the 
floor  and  passing  along  it  to  the  foul-air  register.  The  hot-air 
register  should  be  a  sufficient  distance  from  the  foul-air  register 
so  that  the  hot  air  will  not  pass  directly  to  the  foul-air  flue. 

A  cheap  foul-air  flue  can  be  made  by  having  a  register  in  the 
baseboard  opening  into  the  space  between  the  studding,  select- 
ing a  space  that  is  open  to  the  attic.  A  ventilator  placed  on 
the  roof  discharges  the  air  from  the  attic.  No  two  rooms  should 
be  connected  to  the  same  studding  space.  A  still  better  arrange- 
ment is  to  extend  each  flue  separately  to  the  ventilator. 

The  area  of  the  foul-air  flues  should  be  at  least  80  per  cent, 
of  that  of  the  warm-air  flues  and  they  are  often  made  equal  in 
area  to  the  latter. 

41.  Forced  Circulation. — Furnace  systems  are  sometimes  in- 
stalled in  which  the  circulation  is  produced  by  a  fan.     The 
principal  advantage  of  such  an  arrangement  is  that  the  cir- 
culation is  positive  and  is  not  affected  by  weather  conditions. 
The  fan,  usually  of  the  disc  or  propeller  type,  is  placed  in  the 
cold-air  inlet  to  the  furnace  and  jorces  the  air  through  the  furnace 
and  thence  through  the  hot-air  pipes  to  the  rooms.     Furnace 
systems  with  forced  circulation  are  used  principally  where  a 
considerable  amount  of  air  is  required  for  ventilation  and  where 
an  outfit  is  desired  of  lower  first  cost  than  an  ordinary  fan  system . 

42.  Pipeless  Furnaces. — One  type  of  furnace  which  is  some- 
times used  in  small  houses  is  the  so-called  "pipeless"  furnace 
system.     In  this  system  a  single  register  is  used,  located  immedi- 
ately above  the  furnace,  and  consisting  of  two  sections,  one 


HOT-AIR  FURNACE  HEATING 


47 


section  supplying  hot  air  and  the  other  section  being  con- 
nected to  a  re-circulating  duct  leading  back  to  the  base  of  the 
furnace.  It  is  evident  that  with  such  an  arrangement  the 
room  above  the  furnace  will  receive  the  greatest  amount  of 
heat  and  that  all  the  other  rooms  can  receive  heat  only  by  the 
natural  circulation  of  air  through  them.  The  advantage  of  the 
pipeless  furnace  is  its  low  cost.  It  is  strictly  limited  to  very 
small  houses  or  bungalows  and  is  not  successful  if  installed  out- 
side of  this  field. 

43.  Combination  System. — In  the  effort  to  eliminate  some  of 
the  fundamental  disadvantages  of  the  hot  air  furnace,  a  system 
is  sometimes  used  consisting  of  a  combination  of  a  hot  water 
system  with  an  ordinary  hot  air-furnace  system.     The  rooms 
farthest  from  the  furnace  or  on  the  exposed  side  of  the  build- 
ing are  heated  by  hot  water  radiators  while  those  near  the  furnace 
are  heated  by  hot  air.     The  furnace  is  quite  similar  to  the  ordi- 
nary type,  with  the  addition  of  a  water  heating  element,  usually 
in  the  form  of   a  coil  in  the  fire  pot.     This  system  is  some- 
what lower  in   cost  than  a  straight  hot  water  system  and  if 
properly  installed  is  satisfactory.     It  has  not  come  into  general 
use. 

44.  Test  of  Hot-air  Furnace. — The  following  is  a   summary 
of  the  results  of  a  heat  analysis  of  a  hot-air  furnace  made  at 
the  University  of  Michigan.1 


Test  No. 


11 


2  Length  of  test  —  hours  

30  00 

31  00 

3  Number  of  firings 

2  00 

4  00 

5  Inlet  temperature  of  air  

50  60 

39  60 

6  Average  temperature  of  heated  air 

113  70 

109  20 

7  Temp,  of  wet-bulb  thermometer 

70  80 

64  70 

8  Temperature  of  dry-bulb  thermometer  
9  Humidity,  per  cent  

112.00 
11  00 

107.70 

7  00 

12  Volume  of  air  delivered,  cubic  feet  per  minute  . 
14  Temperature  of  gases  over  fire,  deg.  F  
15  Temperature  of  gases  in  breeching,  deg.  F.  .  . 
16  Draft  in  breeching,  inches  of  water  
17  CO->  content  of  flue  eases.  ner  cent.  . 

1,110.00 

309  00 
0.07 
10.26 

1,284.00 
691.00 
318  40 
0.07G 
8.10 

iaHeat  Analysis  of  a  Hot-air  Furnace,"  by  JOHN  R.  ALLEN,   Trans. 
A/S.  H.  &  V.  E.,  1916. 


48 


HEATING  AND  VENTILATION 


Test  No. 

7 

11 

21  Kind  of  fuel  

Mixed  stove 

and  ctrir 

Gas  coke 

22  Total  weight  of  fuel  fired  
23  Total  weight  of  ash  and  refuse  

anthracite 
255.00 
37  00 

330.50 
16  50 

24  Proximate  analysis  of  fuel,  per  cent. 
Moisture  

0  78 

6  00 

Volatile     

4  75 

3  60 

Fixed  carbon  

88  61 

86  10 

Ash  

12  86 

4  30 

26  Heat  value  per  pound  as  fired  

12,856  00 

13026  00 

28  Total   water   evaporated    from    water   pan, 
pounds  

62  00 

123  00 

Heat  balance,  per  cent. 
43  Heat  input  in  fuel 

100  00 

100  00 

44  Heat  absorbed  by  air  

61  60 

63  00 

45  Heat  given  to  water 

2  05 

3  10 

46  Heat  given  to  air,  gross  
47  Heat  lost  up  the  stack  
48  Heat  lost  in  unburned  fuel 

63.65 
11.65 
1  60 

66.10 
13.50 
0  70 

49  Heat  lost  from  furnace  by  radiation  
50  Unaccounted-for  losses  

51  Efficiency  —  net  (Item  46)  per  cent  

11.00 
12.10 

63  65 

8.83 
10.87 

66  10 

52  Efficiency—  gross  (Items  46  +  49  +  ^  of  50) 
per  cent   

80  70 

80  36 

It  will  be  noted  that  the  heat  given  up  to  the  air  passing 
through  the  furnace  is  from  63  to  66  per  cent,  of  the  heat  input 
in  the  fuel.  In  most  installations,  however,  the  heat  radiated 
from  the  furnace  is  largely  utilized,  making  the  " gross"  efficiency 
about  80  per  cent. 

Problem 

1.  Compute  the  required  size  of  the  leaders,  risers,  and  wall  registers  for 
the  following  rooms. 


Room  No. 
1 
2 
3 
4 


Heat  loss  from  room 

16,000 
10,800 

8,700 

5,000 


Floor 

First 
Second 
Third 
Second 


A 


CHAPTER  V 
PROPERTIES  OF  STEAM 

45.  The  Formation  of  Steam. — The  different  types  of  heating 
systems  discussed  in  Chapter  III  owe  most  of  their  characteristic 
features  to  the  element  used  to  convey  the  heat  from  the  boiler 
or  furnace  to  the  rooms.  Perhaps  the  most  important  is  the 
steam  heating  system,  in  which  steam  serves  as  the  conveying 
medium.  Before  taking  up  the  design  of  steam  heating  systems, 
it  is  necessary  to  study  the  nature  and  properties  of  steam. 

Many  substances  can  exist  in  more  than  one  state  Under  the 
proper  conditions  of  temperature  and  pressure.  Water  exists  as 
ice  at  low  temperatures  and  as  steam  at  higher  temperatures,  the 
temperature  depending  upon  the  pressure.  If  we  apply  heat  to  a 
vessel  partly  filled  with  cold  water,  the  temperature  of  the  water 
will  rise  until  a  certain  temperature  is  reached,  at  which  small 
particles  of  water  are  changed  into  steam.  The  steam  bubbles 
rise  through  the  mass  of  water  and  escape  from  the  surface.  The 
water  is  then  said  to  boil.  The  temperature  at  which  the  water 
boils  depends  upon  the  pressure  in  the  vessel.  If  the  pressure 
is  raised  as  by  partly  closing  the  outlet,  the  temperature  of 
the  water  will  rise  to  the  point  corresponding  to  the  existing 
pressure. 

Steam  when  still  in  contact  with  the  water  from  which  it  is 
produced  remains  at  the  temperature  corresponding  to  its  pres- 
sure and  under  this  condition  the  steam  is  said  to  be  saturated. 
If  it  is  removed  from  contact  with  the  water  and  further  heated, 
its  temperature  will  rise  and  the  steam  will  then  be  superheated. 

46.  Superheated  Steam. — Superheated  steam  is  steam  at  a 
temperature  higher  than  the  temperature  of  the  boiling  point 
corresponding  to  the  pressure.  If  water  were  to  be  intimately 
mixed  with  superheated  steam  some  of  the  heat  in  the  steam 
would  be  used  in  evaporating  the  water  and  the  temperature  of 
the  steam  would  be  lowered.  If  sufficient  water  were  added  the 
superheat  would  be  entirely  used  up  in  evaporating  the  water  and 
the  steam  would  then  be  saturated.  Superheated  steam  can 
4  49 


50  HEATING  AND  VENTILATION 

have  any  temperature  higher  than  that  of  the  boiling  point. 
When  raised  to  any  temperature  considerably  above  the  boiling 
point  it  follows  very  closely  the  laws  of  a  perfect  gas  and  may  be 
treated  as  a  perfect  gas. 

47.  Saturated  Steam. — When  steam  is  at  the  temperature  of 
the  boiling  point  corresponding  to  its  pressure  it  is  said  to  be 
saturated.     If  this  saturated  steam  contains  no  suspended  mois- 
ture it  is  said  to  be  dry  saturated  steam,  or  in  other  words,  dry 
saturated  steam  is  steam  at  the  temperature  of  the  boiling  point 
and  containing  no  water  in  suspension.     If  heat  is  added  to  dry 
saturated  steam,  not  in  the  presence  of  water,  it  will  become 
superheated.     If  heat  is  taken  away  from  dry  saturated  steam  it 
will  become  wet  steam.     The  steam  produced  in  most  heating 
boilers  is  saturated  steam  and  nearly  always  contains  moisture, 
so  that  the  substance  used  as  a  heating  medium  is  really  a  mixture 
of  steam  and  water.     Steam  at  a  pressure  equal  to  or  slightly 
above  atmosphere  is  commonly  known  as  vapor.     It  should  be 
remembered,  however,  that  the  difference  between  vapor  and 
steam  is  merely  one  of  pressure,  and  that  vapor  is  in  no  sense  a 
separate  state  of  the  substance.     Dry  saturated  steam  is  not  a 
perfect  gas  and  the  relations  of  its  pressure,  volume,  and  tem- 
perature do  not  follow  any  simple  law  but  have  been  determined 
by  experiment.     The  properties  of  dry  saturated  steam  were 
originally  determined  by  Regnault  between  60  and  70  years  ago, 
and  so  carefully  was  his  work  done  that  no  errors  in  his  results 
were  apparent  until  within  very  recent  years,  when  the  great 
difficulty  of  obtaining  steam  which  is  exactly  dry  and  saturated 
became  appreciated,  and  new  experiments  by  various  scientists 
proved  that  Regnault 's  results  were  slightly  high  at  some  pres- 
sures and  slightly  low  at  others. 

48.  Properties  of  Steam. — The  heat  used  in  the  formation  of 
one  pound  of  superheated  steam  at  any  pressure  from  water  at 
32°  may  be  divided  into  three  parts:  (a)  the  heat  of  the  liquid, 
which  is  the  heat  required  to  raise  the  temperature  of  the  water 
from  32°  to  the  temperature  of  the  boiling  point;  (6)  the  latent 
heat  of  vaporization,  which  is  the  amount  required. to  change 
one  pound  of  water  at  the  temperature  of  the  boiling  point  to 
dry  saturated  steam  at  the  same  temperature;  and  (c)  the  "heat 
of  superheat"  or,  more  simply,  the  superheat,  which  is  the  heat 
added  to  one  pound  of  steam  to  raise  it  from  the  boiling  point 
temperature  to  the  final  temperature. 


PROPERTIES  OF  STEAM  51 

49.  Heat  of  the  Liquid. — The  heat  of  the  liquid  may  be  deter- 
mined for  any  boiling  point   temperature   by   the   expression 

h  =  c(t  -  32) 
in  which 

h  =  the  heat  of  the  liquid. 
t  =  the  boiling  point  temperature. 
c  =  the  specific  heat  of  water. 

For  approximate  results  c  may  be  taken  as  =  1. 

The  change  in  the  volume  of  the  water  during  the  increase  in 
temperature  is  extremely  small,  and  the  amount  of  external  work 
done  may  be  neglected  and  all  of  the  heat  of  the  liquid  may  be 
considered  as  going  to  increase  the  heat  energy  of  the  water. 

The  heat  of  the  liquid,  together  with  the  other  properties  of 
saturated  steam,  is  given  in  Table  XI  for  various  steam  pressures. 
This  table  is  condensed  from  Marks  and  Davis'  complete  tables 
which  are  generally  accepted  as  being  accurate. 

50.  Latent  Heat. — The  latent  heat  of  steam  has  been  defined  as 
the  heat  required  to  convert  one  pound  of  water  at  the  tempera- 
ture of  the  boiling  point  into  dry  saturated  steam  at  the  same 
temperature.     Experiments  show  that  the  latent  heat,  usually 
designated  by  L,  diminishes  as  the  pressure  increases. 

When  water  is  changed  into  steam,  the  volume  is  greatly 
increased,  so  that  a  considerable  portion  of  the  latent  heat  is 
used  in  doing  external  work.  The  remainder  may  be  considered 
as  being  utilized  in  changing  the  physical  state  of  the  water. 
Let  P  be  the  pressure  at  which  the  steam  is  generated,  V  the  vol- 
ume of  one  pound  of  steam,  and  v  the  volume  of  one  pound  of 
water;  then  the  external  work  done  is  equal  to 

P(V  -  ») 

At  212°  the  external  work  done  in  producing  one  pound  of  steam 
is  equivalent  to  73  B.t.u.  or  about  one-thirteenth  of  the  latent 
heat. 

Experiments  show  that  the  latent  heat  of  steam  diminishes 
about  0.695  heat  units  for  each  degree  that  the  temperature  of  the 
boiling  point  is  increased.  If  t  be  the  temperature  of  the  boiling 
point,  then,  approximately, 

L  =  1072.6  -  0.695(*  -  32) 

When  steam  condenses  the  same  amount  of  heat  is  given  up  as 
was  required  to  produce  it.  In  the  steam  heating  system  the 


52  HEATING  AND  VENTILATION 

latent  heat  is  added  to  the  water  in  the  boiler,  converting  it 
into  steam.  The  steam  is  conducted  to  the  radiators  in  which 
it  condenses.  In  condensing,  it  gives  up  its  latent  heat  which 
goes  to  warm  the  room. 

51.  Total  Heat  of  Steam.  —  The  total  heat  of  dry  saturated 
steam  is  the  heat  required  to  change  one  pound  of  water  at  32° 
into  dry  saturated  steam.  This  quantity  will  be  designated  by 
H}  and 

H  =  h  +L 

The  experimental  results  given  in  the  table  for  the  value  of  the 
total  heat  may  be  approximated  very  closely  by  means  of  the 
formula 

H  =  1072.6  +  0.305(£  -  32) 

It  is  more  accurate,  however,  to  take  the  values  of  the  total  heat 
from  the  tables  than  it  is  to  compute  them  from  the  formula. 
The  total  heat  in  one  pound  of  steam  under  any  condition  of  mois- 
ture or  superheat  is  the  amount  of  heat  required  to  change  it 
from  water  at  32°  to  its  existing  condition. 

When  steam  contains  entrained  water  the  percentage  by  weight 
of  dry  steam  in  the  mixture  is  termed  the  quality  of  the  steam. 
If  we  let  q  represent  the  quality  of  the  steam,  then  the  latent  heat 
in  one  pound  of  wet  steam  equals 

qL 
100 

and  the  total  heat  in  one  pound  of  wet  steam  equals 


52.  Steam  Tables.  —  The  following  table  shows  the  properties 
of  dry  saturated  steam.  More  complete  tables  will  be  found  in 
Marks  and  Davis'  "  Steam  Tables"  and  in  the  engineering 
handbooks.  Column  1  gives  the  absolute  pressure  of  the  steam 
in  pounds  per  square  inch.  Absolute  pressure  is  the  pressure 
shown  on  the  steam  gage  plus  the  atmospheric  or  barometric 
pressure.  For  sea-level  barometer  the  atmospheric  pressure  is 
14.7  pounds  per  square  inch.  Column  2  gives  the  corresponding 
temperature  of  the  steam  in  degrees  Fahrenheit.  Column  3  gives 
the  heat  of  the  liquid,  and  column  4  gives  the  latent  heat. 
Column  5  gives  the  total  heat  of  the  steam  and  is  the  sum  of  the 
quantities  in  columns  3  and  4.  Column  6  is  the  volume  of  one 


PROPERTIES  OF  STEAM 


53 


pound  of  dry  saturated  steam  at  the  different  pressures.     Column 
7  is  the  weight  of  one  cubic  foot  of  steam  at  the  different  pressures. 

TABLE  XI. — PROPERTIES  OF  SATURATED  STEAM1 


1 

Absolute 
pressure, 
Ib.  per 
sq.  in. 

2 
Temp., 
deg.  F. 

3 

Heat 
of  the 
liquid 

4 
Latent 
heat  of 
evap. 

5 

Total 
heat  of 
the  steam 

6 

Sp.  vol., 
cu.  ft. 
per  Ib. 

7 
Density, 
Ib.  per 
cu.  ft. 

P 

t 

h 

L 

H 

V 

1/D 

10 

193.22 

161.1 

982.0 

1,143.1 

38.38 

0.02606 

11 

197.75 

165.7 

979.2 

1,144.9 

35.10 

0.02849 

12 

201.96 

169.9 

976.6 

1,146.5 

32.36 

0.03090 

13 

205  .  87 

173.8 

974.2 

1,148.0 

30.03 

0.03330 

14 

209  .  55 

177.5 

971.9 

1,149.4 

28.02 

0.03569 

15 

213.00 

181.0 

969.7 

1,150.7 

26.27 

0.03806 

16 

216.30 

184.4 

967.6 

1,152.0 

24.79 

0.04042 

17 

219.40 

187.5 

965.6 

1,153.1 

23.38 

0.04279 

18 

222.40 

190.5 

963.7 

1,154.2 

22.16 

0.04512 

19 

225  .  20 

193.4 

961.8 

1,155.2 

21.07 

0.04746 

20 

228.00 

196.1 

960.0 

1,156.2 

20.08 

0.04980 

21 

230.60 

198.8 

958.3 

1,157.1 

19.18 

0.05213 

22 

233.10 

201.3 

956.7 

1,158.0 

18.37 

0.05445 

23 

235.50 

203.8 

955.1 

1,158.8 

17.62 

0.05676 

24 

237.80 

206.1 

953.5 

1,159.6 

16.93 

0.05907 

25 

240.10 

208.4 

952.0 

1,160.4 

16.30 

0.0614 

30 

250.30 

218.8 

945.1 

1,163.9 

13.74 

0.0728 

35 

259.30 

227.9 

938.9 

1,166.8 

11.89 

0.0841 

40 

267.30 

236.1 

933.3 

1,169.4 

10.49 

0.0953 

45 

274  .  50 

243.4 

928.2 

1,171.6 

9.39 

0.1065 

50 

281.00 

250.1 

923.5 

1,173.6 

8.51 

0.1175 

55 

287.10 

256.3 

919.0 

1,175.4 

7.78 

0.1285 

60 

292  .  70 

262.1 

914.9 

1,177.0 

7.17 

0.1394 

65 

298.00 

267.5 

911.0 

1,178.5 

6.65 

0.1503 

70 

302  .  90 

272.6 

907.2 

1,179.8 

6.20 

0.1612 

75 

307  .  90 

277.4 

903  .  7 

1,181.1 

5.81 

0.1721 

80 

312.00 

282.0 

900.3 

1,182.3 

5.47 

0.1829 

85 

316.30 

286.3 

897.1 

1,183.4 

5.16 

0.1937 

90 

320  .  30 

290.5 

893.9 

1,184.4 

4.89 

0.2044 

95 

324.10 

294.5 

890.9 

1,185.4 

4.65 

0.2151 

100 

327.80 

_  298.3 

888.0 

1,186.3 

4.429 

0  .  2258 

105 

331.40 

302.0 

885.2 

1,187.2 

4.230 

0.2365 

110 

334  .  80 

305.5 

882.5 

1,188.0 

4.047 

0.2472 

115 

338.10 

309.0 

879.8 

1,188.8 

3.880 

0.2577 

120 

341.30 

312.3 

877.2 

1,189.6 

3.726 

0.2683 

125 

344.40 

315.5 

874.7 

1,190.3 

3.583 

0.2791 

130 

347.40 

318.6 

872.3 

1,191.0 

3.452 

0.2897 

135 

350.30 

321.7 

869.9 

1,191.6 

3.331 

0.3002 

MARKS  and  DAVIS'  "Steam  Tables  and  Diagrams." 


54  HEATING  AND  VENTILATION 

53.  Mechanical  Mixtures. — Problems  involving  the  resulting 
temperature  and  final  condition  when  various  substances  at 
different  temperatures  are  mixed  mechanically  are  often  met 
with  in  heating  work.  They  are  best  treated  by  first  determining 
the  heat  in  B.t.u.  that  would  be  available  for  use  if  the  tempera- 
ture of  all  of  the  substances  were  brought  to  32°F.,  and  using  this 
heat  (positive  or  negative)  to  raise  (or  lower)  the  total  weight 
of  the  mixture  to  its  final  temperature  and  condition.  Another 
method  of  solving  such  problems  is  by  equating  the  heat 
absorbed  to  the  heat  rejected  and  solving  for  t,  the  resulting  tem- 
perature. It  is  often  difficult  to  decide  upon  which  side  of  the 
equation  a  material  should  be  placed.  In  such  a  case  a  trial  cal- 
culation should  be  made,  and  the  temperature  determined  by 
the  trial  will  settle  this  question. 

In  a  mixture  of  substances  which  pass  through  a  change  of 
state  during  the  mixing  process  it  is  almost  necessary  to  make  a 
trial  calculation.  Take  for  example  a  mixture  of  steam  with 
other  substances.  The  steam  may  all  be  condensed  and  the 
resulting  water  cooled  also;  the  steam  may  all  be  condensed  only; 
or  the  steam  may  be  only  partially  condensed.  The  equations 
in  each  case  would  be  different. 

If  one  pound  of  dry  saturated  steam  at  a  temperature  ti  is  con- 
densed and  then  the  temperature  of  the  condensed  steam  is  low- 
ered to  a  temperature  t2)  the  amount  of  heat  Hf  given  off  would  be 

H'  =  L!  +  c(«i  -  t*) 

where  LI  is  the  latent  heat  corresponding  to  the  temperature  t\ 
and  c  is  the  specific  heat  of  water.  If  the  steam  were  condensed 
only,  the  heat  given  off  would  be 

H'  =  L1 

and  the  temperature  of  the  mixture  is  the  temperature  corre- 
sponding to  the  pressure.  If  the  steam  is  only  partly  condensed 
let  qf  equal  the  per  cent,  of  steam  condensed.  Then 

loo 

and  the  temperature  of  the  mixture  is  the  temperature  corre- 
sponding to  the  pressure. 

The  general  laws  of  thermodynamics  do  not  apply  in  the  case 
of  mixtures  as  the  equations  become  discontinuous. 

The  general  expression  for  heat  absorbed  in  passing  from  a 
solid  to  a  gaseous  state  may  be  stated  as  follows: 


PROPERTIES  OF  STEAM  55 

Let  ci,  c2,  c3  be  the  specific  heats  of  the  material  in  the  solid, 
liquid,  and  gaseous  states,  respectively.  Let  w  be  the  weight  of 
the  material,  t  the  initial  temperature,  t\  the  temperature  of  the 
melting  point,  U  the  temperature  of  the  boiling  point,  £3  the  final 
temperature,  Hf  the  heat  of  liquefaction,  and  L  the  heat  of 
vaporization.  Then 

H'  =  M;[CI(*I  -t)  +  Hf  +  c2(t2  -  «  +  L  +  c3fe  -  *2)1 

Example.-  -Find  the  final  temperature  and  condition  of  the  mixture 
after  mixing  10  pounds  of  ice  at  20°,  20  pounds  of  water  at  50°  and  2  pounds 
of  steam  at  atmospheric  pressure.  Mixture  takes  place  at  the  pressure  of 
the  steam.  The  specific  heat  of  ice  may  be  taken  as  0.5  and  the  heat  of 
liquefaction  as  144  B.t.u. 

FIRST  METHOD 
Solution. — 

Heat  to  raise  ice  to  32°  =  10  X  0.5(32  -  20)  =60.0 

Heat  to  melt  ice  =  10  X  144  =  1440 


Total  heat  necessary  to  change  the  ice  to  water  at  32°      =  1500  B.t.u. 

Heat  given  up  by  water  when  temperature  is  lowered  to 

32°  =  20  X  (50  -  32)  =    360.0 

Heat  in  steam  above  32°  (from  tables)  =  2  X  1150.3       =  2300.6 


Total  heat  given  up  in  lowering  water  and  steam  to  32°    =  2660.6  B.t.u. 

Heat  available  for  use  =  2660.6  -  1500  =  1160.6  B.t.u. 

Degrees  this  heat  will  raise  the  mixture  1160 . 6  -=-32  =  36 . 3 

.'.  Final  temperature  of  mixture  =  36.3  +  32  =  68.3°F. 
Ana.     32  pounds  water  at  68.3°F. 

SECOND  METHOD 

Assume  that  the  steam  is  all  condensed  and  that  the  final  temperature 
of  the  mixture  is  t.  Then  the  heat  necessary  to  raise  the  ice  to  the  melting 
point  equals 

10  X  0.5(32  -  20) 

The  heat  necessary  to  melt  the  ice  equals  10  X  144;  the  heat  necessary  to 
raise  the  melted  ice  to  the  temperature  of  the  mixture  equals  W(t  —  32);  the 
heat  necessary  to  raise  the  water  to  the  temperature  of  the  mixture  equals 
20  (t  —  50);  the  heat  given  up  by  the  steam  in  changing  to  water  at  the 
temperature  of  the  boiling  point  equals  2  X  970.4,  and  the  heat  given  up 
by  the  condensed  steam  when  its  temperature  is  lowered  to  the  temperature 
of  the  mixture  equals  2(212  -  t). 

Combining  the  preceding  parts  into  one  equation,  we  have 

10X0.5(32-20) +10X144  +  10(^-32) +20(*-50)  =2X970.4+2(212-0 


56  HEATING  AND  VENTILATION 

60  +  1440  +  10*  -  320  +  20*  -  1000  =  1940.8  +  424  -  2* 

32*  =  2184.8 
t  =  68.3° 

Since  t  is  less  than  the  temperature  of  the  boiling  point  corresponding  tc 
the  pressure  at  which  the  mixture  takes  place,  all  the  steam  is  condensed. 
Ans.  32  pounds  water  at  68.3°F. 

Example. — Find  the  resulting  temperature  and  condition  after  mixing  10 
pounds  of  ice  at  20°,  20  pounds  of  water  at  50°,  40  pounds  of  air  at  82°,  and 
20  pounds  of  steam  at  100  pounds  gage  pressure  and  containing  2  per  cent, 
moisture.  Mixture  takes  place  at  the  pressure  of  the  steam. 

FIRST  METHOD 

Solution. — 

10  X  0.5(32  -  20)  60 

10  X  144  =      1440 


1500  B.t.u.  =  heat  to  raise  ice  to  water  at 

32°. 

20  X  (50  -  32)  =       360 

40  X  0.2415(82  -  32)         =       483 
20(308.8  +  0.98  X  880.0)  =  23,424 

24,267  B.t.u.  =  heat  given  up  by  air,  water, 
1,500  and  steam. 


22,767  B.t.u.  =  heat  available. 
40  X  0.2415(337.9  -  32)    =    2,955  B.t.u.  =  heat  to  raise  air  to  337.9°. 


19,812  B.t.u.  =  heat    available    to    raise    the 

water. 
50  X  308.8  =  15,440  B.t.u.  =  heat  to  raise  water  to  337.9° 


4,372  B.t.u.  =  heat    available    to    evaporate 
water. 

4372 

g8Q  Q  =  4.97  pounds  steam. 

Ans.     40.00  pounds  air  \ 

45.03  pounds  water  I   at  337.9°. 

4.97  pounds  dry  saturated  steam  J 

SECOND  METHOD 

Assume  the  steam  to  be  all  condensed  and  let  the  temperature  of  the 
mixture  be  t°.  Equating  the  heat  gained  by  the  ice,  water,  and  air,  and  the 
heat  lost  by  the  steam,  we  have 

10  X  0.5(32  -  20)  +  10  X  144  +  10 (t  -  32)  +  20(*  -  50)  +  40  X  0.2415 
(t  -  32)  =  20  X  0.98  X  880.0  +  20(337.9  -  0 

60  +  1440  +  lOt  -  320  +  20*  -  1000  +  9.7*  -  792  =  17,248  +  6758  —  20* 


PROPERTIES  OF  STEAM  57 

59.5J  =  24,618 
t  =  413.7°F. 

This  result  is  of  course  absurd,  as  the  temperature  of  the  mixture  cannot 
be  higher  than  the  temperature  of  the  boiling  point  corresponding  to  the 
pressure  at  which  the  mixture  'takes  place.  Therefore,  our  assumption 
that  all  the  steam  is  condensed  must  be  wrong,  and  we  know  that  part  of 
it  remains  in  the  form  of  steam,  and  hence  the  temperature  of  the  mixture 
is  equal  to  the  temperature  of  the  boiling  point  corresponding  to  the  pressure 
at  which  the  substances  are  mixed. 

Then,  substituting  for  t  its  value,  and  letting  x  represent  the  number  of 
pounds  of  steam  condensed,  we  have 

10  X  0.5(32  -  20)  +  10  X  144  +  10(337.9  -  32)  +  20(337.9  -  50)  + 

40  X  0.2415(337.9  -  82)  =  880.03= 

60  +  1440  +  3059  +  5758  +  2472  =  880.0z 
880.0z  =  12,789 

x  =  14.53  pounds  condensed. 

20  X  0.98  =  19.6  pounds  =  original  weight  of  dry  steam. 

Ans.     40  pounds  air 

10  +  20  +  (20  -  19.6)  +  14.53  =  44.93  pounds  water  [  at  337.9°. 
19.6  —  14.53  =  5.07  pounds  dry  saturated  steam  J 

The  difference  between  the  results  obtained  in  these  two  methods  of  work- 
ing this  problem  is  due  to  the  fact  that  in  the  first  method  we  took  account 
of  the  variation  in  the  specific  heat  of  water  by  using  the  heat  of  the  liquid, 
h,  from  the  tables,  in  place  of  (t  —  32)  wherever  possible,  while  in  the  second 
method  we  assumed  this  specific  heat  to  be  constant  and  equal  to  1. 

Example. — Find  the  resulting  temperature  and  condition  after  mixing  10 
pounds  of  ice  at  20°,  20  pounds  of  water  at  50°,  and  30  pounds  of  steam  at 
100  pounds  pressure  and  400°  temperature.  Mixture  takes  place  at  25 
pounds  pressure. 

FIRST  METHOD 
Solution. — 

10  X  0.5(32  -  20)  60 

10  X  144  =     1,440 


1,500  B.t.u.  =  heat  to  raise  ice  to  water  at  32°. 
20  X  (50  -  32)  =       360 

*30  X  0.53(400  -  337.9)  =        987 
30  X  1188.8  =  35,664 


37,013  B.t.u.  =  heat   given   up   by   water   and 

steam. 
1,500 

35,513  B.t.u.  =  heat  available. 
60  X  235.6  =  14,136  B.t.u.  =  heat  to  raise  water  to  266.8°. 

21,377  B.t.u.  =  heat     available     to    evaporate 

water. 
*0.53  =  specific  heat  of  superheated  steam. 


58  HEATING  AND  VENTILATION    . 

21  377 

QOQ  a    =  22.89  pounds  steam. 

Ans.     37.11  pounds  water  }        ^QQ  gOF 

22.89  pounds  dry  saturated  steam  / 

SECOND  METHOD 

Assume  the  steam  to  be  all  condensed  and  let  the  temperature  of  the 
mixture  be  t°.  Then 

10  X  0.5(32  -  20)  +  10  X  144  +  lQ(t  -  32)  +  20(t  -  50)   =  30  X  0.53 

(400  -  337.9)  +  30  X  880.0  +  30(337.9  -  t) 

60  +  1440  +  10*  -  320  +  20t  -  1000  =  987  +26,400  +  10,137  -  30t 

60«  =  37,344 
t  =  622.4° 

This  result  is,  of  course,  impossible  and  we  see  at  once  that  only  part  of 
the  steam  is  condensed,  and  that  the  temperature  of  the  mixture  must  be  that 
of  the  boiling  point  corresponding  to  the  pressure  at  which  the '  mixture 
takes  place. 

This  problem  differs  from  the  previous  ones  in  that  the  pressure  of  the 
mixture  is  different  from  the  original  steam  pressure,  and  we  must  proceed 
in  a  slightly  different  manner. 

Assume  for  the  moment  that  the  steam  has  all  been  condensed  and  that 
we  have  60  pounds  of  water  at  622. 4°F.  Then  assume  that  the  temperature 
of  the  water  is  dropped  to  the  temperature  of  the  boiling  point  (266.8°) 
corresponding  to  the  pressure  (25  pounds)  at  which  the  mixture  is  made. 
Each  pound  will  give  up,  approximately  (622.4  —  266.8)  B.t.u.  This  heat 
can  then  be  used  to  re-evaporate  part  of  the  water.  Therefore,  since  the 
latent  heat  corresponding  to  25  pounds  is  933.6,  we  have 

60(622.4  -  266.8)        60  X  355.6        21,330 

933.6  -933:6—     =    933^  =  22'85  pounds 

Ans.     37.15  pounds  water 

22.85  pounds  dry  saturated  steam 

Problems 

1.  Required  the  temperature  after  mixing  3  pounds  of  water  at  100°F., 
10  pounds  of  alcohol  at  40°F.,  and  20  pounds  of  mercury  at  60°F. 

2.  Required  the  temperature  and  condition  after  mixing  5  pounds  of  ice 
at  10°F.  with  12  pounds  of  water  at  60°F.1 

3.  Required  the  temperature  and  condition  after  mixing  10  pounds  of  ice 
at  15°F.  with  1  pound  of  water  at  212°F, 

4.  Required  the  temperature  and  condition  of  the  mixture  after  mixing 
5  pounds  of  steam  at  212°F.  with  20  pounds  of  water  at  60°F. 

5.  One  pound  of  ice2  at  32°  is  mixed  with  10  pounds  of  water  at  50°  and 

1  Specific  heat  of  ice  equals  0.5. 

2  Latent  heat  of  fusion  of  ice  =  144  B.t.u. 


PROPERTIES  OF  STEAM  59 

20  pounds  of  steam  at  212°.     What  is  the  temperature  and  condition  of  the 
resulting  mixture? 

6.  Ten  pounds  of  steam  at  212°  are  mixed  with  50  pounds  of  water  at 
60°  and  2  pounds  of  ice  at  32°.     What  will  be  the  resulting  temperature  and 
condition  of  the  mixture? 

7.  Ten  pounds  of  steam  at  atmospheric  pressure,  5  pounds  of  water  at 
50°  and  10  pounds  of  ice  at  32°  are  mixed  together,     (a)  What  will  be  the 
resulting  temperature  of  the  mixture?     (b)  What  will  the  condition  of  the 
mixture  be?     (c)  If  the  steam  is  not  all  condensed,  determine  what  per 
cent,  of  the  steam  will  be  condensed. 

8.  Five  pounds  of  steam  at  atmospheric  pressure,  10  pounds  of  water  at 
60°,  and  2  pounds  of  ice  at  20°  are  mixed  at  atmospheric  pressure.     What 
will  be  the  resulting  temperature? 

9.  Ten  pounds  of  ice  at  10°,  20  pounds  of  water  at  60°  and  5  pounds  of 
steam  at  atmospheric  pressure  are  mixed  at  atmospheric  pressure.     Find 
the  resulting  temperature  and  condition  of  the  mixture. 

10.  Twenty  pounds  of  steam  at  atmospheric  pressure,  10  pounds  of  water 
at  60°  and  50  pounds  of  air  at  100°  are  mixed  together  at  the  pressure  of  the 
steam,     (a)  What  will  be  the  resulting  temperature?     (b)  If  the  steam  is 
not  all  condensed,  determine  what  per  cent,  of  the  steam  will  be  condensed. 

11.  A  mixture  is  made  of  10  pounds  of  steam  at  atmospheric  pressure, 
5  pounds  of  ice  at  20°,  10  pounds  of  water  at  50°,  30  pounds  of  air  at  60°. 
(a)  What  will  be  the  temperature  of  the  resulting  mixture?     (b)  What  will 
be  the  percentages  by  weight  of  air,  steam,  and  water  in  the  mixture? 

12.  What  would  be  the  resulting  temperature  and  condition  of  a  mixture 
of  10  pounds  of  water  at  40°,  20  pounds  of  water  at  60°,  and  8  pounds  of 
steam  at  5  pounds  pressure?     Mixture  takes  place  at  5  pounds  pressure. 

13.  Ten  pounds  of  steam  at  5  pounds  pressure,  1  pound  of  ice  at  32°,  and 
20  pounds  of  water  at  60°  are  mixed  at  5  pounds  pressure.     What  will  be 
the  temperature  and  condition  of  the  resulting  mixture? 

14.  Five  pounds  of  ice  at  5°,  10  pounds  of  water  at  50°,  20  pounds  of  air 
at  80°,  and  5  pounds  of  steam  at  20  pounds  pressure  are  mixed  at  the  pres- 
sure of  the  steam.     Find  the  resulting  temperature  and  condition  of  the 
mixture. 

15.  Required  the  temperature  and  condition  of  the  mixture  after  mixing 
10  pounds  of  steam  at  a  pressure  of  30  pounds  absolute  and  a  temperature 
of  250.3°F.,  2  pounds  of  ice  at  10°F.,  and  20  pounds  of  water  at  40°F.     Mix- 
ture takes  place  at  the  pressure  of  the  steam. 

16.  Fifty  pounds  of  air  at  100°,  10  pounds  of  steam  at  atmospheric  pres- 
sure, and  10  pounds  of  water  at  60°  are  mixed  at  atmospheric  pressure. 
What  is  the  temperature  of  the  mixture  and  how  much  steam  is  condensed? 

17.  Required  the  final  temperature  and  condition  after  mixing  at  the 
pressure  of  the  air  100  pounds  of  air  at  a  temperature  of  500°  and  a  pressure 
of  100  pounds  absolute,  and  2  pounds  of  steam  at  100  pounds  absolute 
having  a  quality  of  98  per  cent. 

18.  Five  pounds  of  steam  at  5  pounds  gage  pressure  are  mixed  at  atmos- 
pheric pressure  with  10  pounds  of  water  at  60°.     What  is  the  temperature 
and  condition  of  the  resulting  mixture? 

19.  Thirty  pounds  of  water  at  60°,  10  pounds  of  steam  at  115  pounds 


60  HEATING  AND  VENTILATION 

r 

absolute  and  a  temperature  of  400°F.,  and  10  pounds  of  ice  at  20°  are  mixed 
at  atmospheric  pressure.  What  will  the  resulting  temperature  be?  What 
is  the  condition  of  the  mixture? 

20.  Ten  pounds  of  ice  at  20°F.,  18  pounds  of  water  at  80°,  and  10  pounds 
steam  at  75  pounds  pressure  and  90  per  cent,  quality,  are  mixed  at  atmos- 
pheric pressure.     What  is  the  resulting  temperature  and  condition  of  the 
mixture  ? 

21.  Two  pounds  of  steam  at  150  pounds  absolute  and  a  temperature  of 
400°,  5  pounds  of  ice  at  22°,  and  10  pounds  of  water  at  60°  are  mixed  at 
atmospheric  pressure.     Find  the  final  temperature  and  condition  of  mixture. 

22.  Required  the  final  temperature  and  condition  after  mixing  at  atmos- 
pheric pressure  3  pounds  of  ice  at  22°  and  3  pounds  of  steam  at  100  pounds 
pressure  and  containing  2  per  cent,  moisture. 

23.  Find  the  resulting  temperature  and  condition  of  a  mixture  of  10 
pounds  of  steam  at  150  pounds  absolute  and  a  temperature  of  400°F.,  10 
pounds  of  water  at  60°F.,  and  50  pounds  of  air  at  112°F.     Mixture  takes 
place  at  atmospheric  pressure. 

24.  Five  pounds  of  ice  at  0°,  20  pounds  of  water  at  75°,  and  15  pounds  of 
steam  at  50  pounds  absolute  and  95  per  cent,  quality  are  mixed  at  20  pounds 
absolute.     What  is  the  resulting  temperature  and  condition  of  the  mixture? 

26.  How  many  pounds  of  water  will  10  pounds  of  dry  steam  heat  from 
50°  to  150°  if  the  steam  pressure  is  100  pounds  gage? 

26.  If  10  pounds  of  steam  at  100  pounds  gage  raised  93  pounds  of  water 
from  50°  to  140°,  what  per  cent,  of  moisture  is  in  the  steam,  radiation  being 
zero? 

27.  A  pound  of  steam  and  water  occupies  3  cubic  feet  at  110  pounds 
absolute  pressure.     What  is  the  quality  of  the  steam? 


CHAPTER  VI 
RADIATORS 

54.  Classification. — In  a  steam  or  hot-water   heating  system 
the  conveying  medium  absorbs  heat  at  the  boiler  and  then 
flows  to  the  radiators  whose  function  is  to  deliver  the  heat  to  the 
air,  walls,  etc.  of  the  room.     There  are  several  forms  of  radiation, 
the  proper  one  to  be  used  in  any  particular  case  depending  upon 
the  nature  and  use  of  the  building. 

The  selection  of  radiators  of  the  proper  size  for  each  room  in 
the  building  is  very  important.  If  the  radiators  are  too  small  it 
will  be  impossible  in  the  coldest  weather  to  warm  the  building 
to  the  required  temperature  within  a  reasonable  time,  if  at  all. 
On  the  other  hand,  the  installation  of  radiators  of  too  large  a 
size  adds  unnecessarily  to  the  cost  of  the  heating  system,  and 
tends  to  cause  the  rooms  to  be  overheated  during  a  large  part  of 
the  time.  In  order  to  compute  intelligently  the  amount  of 
radiating  surface  required,  it  is  necessary  to  study  the  various 
forms  of  radiation  and  the  factors  affecting  the  rate  of  heat 
transmission  from  each. 

Radiators  may  be  divided  into  three  classes :  (a)  direct  radia- 
tors, (6)  indirect  radiators,  and  (c)  semi-indirect  radiators. 
Direct  radiators;  as  explained  in  Chapter  III,  are  located  in  the 
rooms  to  be  heated,  while  indirect  radiators  are  located  elsewhere 
and  a  current  of  air  conveys  the  heat  from  them  to  the  rooms. 
Semi-indirect  radiators  are  a  combination  of  the  other  two  forms, 
the  radiators  being  installed  in  the  rooms  but  delivering  a  large 
proportion  of  their  heat  output  by  means  of  a  current  of  air 
which  passes  through  them. 

55.  Direct  Cast-iron  Radiators. — Direct  radiators  are  made 
of  cast  iron,  pressed  iron,  and  wrought  iron  or  steel  pipe,  the 
cast-iron  radiator  being  by  far  the  most  common.     It  is  com- 
posed of  several  sections  cast  separately  and  assembled,  the 
number  of  sections  varying  according  to  the  amount  of  surface 
required.     The  sections  are  made  in  several  different  widths  and 
heights  so  that  for  a  radiator  of  a  given  surface,  a  wide  range  of 
shapes  and  sizes  is  available.     The  wider  sections  are  divided 
through  most  of  their  length  by  vertical  slots  into  from  two  to 
six  segments  or  " columns."     The  standard  heights  vary  from 

61 


62 


HEATING  AND  VENTILATION 


15  to  45  inches  but  the  38-inch  height  is  the  one  most  often  used. 
In  Fig.  20  are  shown  several  forms  of  cast-iron  radiators.     Radia- 


i 

ni 


Single  Column 
Radiator 


Two  Column 
Radiator 


Three  Column 
Radiator 


Four  Column  Radiator 


Window  Type 


FIG.  20. 


tors  are   finished   in   several  designs  to  harmonize  with  room 
decorations. 


RADIATORS 


63 


In  general  appearance  the  form  of  radiator  used  for  steam  is 
quite  similar  to  that  used  for  water.  The  two  designs  are  funda- 
mentally different,  however,  in  that  the  sections  of  the  steam 
radiator  are  joined  together  at  the  bottom  only,  while  those  in  a 
hot-water  radiator  are  connected  at  both  top  and  bottom.  Hot- 
water  radiation  may  be  used  for  steam  but  steam  radiation  could 
not  be  satisfactorily  used  for  hot  water  because  air  would  become 
trapped  in  the  top  of  each  of  the  sections,  preventing  the  water 
from  filling  them. 

The  sections  are  joined  by  means  of  nipples.  One  method  is 
to  use  a  smooth  tapered  "push  nipple,"  fitting  into  tapered  holes 
in  the  adjacent  sections.  Draw-bolts  extending  the  full  length  of 


FIG.  21. — Methods  of  assembling  cast-iron  radiators. 

the  radiator  are  used  to  force  the  joints  to  a  tight  fit.  Another 
method  is  to  use  nipples  threaded  with  right  and  left  threads. 
These  nipples  are  cast  with  internal  lugs  and  are  turned  up  by 
means  of  a  special  wrench.  The  two  methods  of  assembling 
are  shown  in  Fig.  21. 

Cast-iron  radiators  are  usually  given  a  hydraulic  pressure  test 
at  the  factory  of  about  120  pounds  per  square  inch.  They  are 
therefore  suitable  for  working  pressures  approaching  this  figure 
but  are  seldom  subjected  to  any  such  pressure  except  in  the  case 
of  hot-water  systems  in  tall  buildings  where  the  hydrostatic 
head  is  high.  The  weight  of  cast-iron  radiators  averages  about  7 
pounds  per  square  foot  of  surface  and  the  internal  volume  is  about 


64 


HEATING  AND  VENTILATION 


30  cubic  inches  per  square  foot  of  surface.  This  internal  volume 
is  largely  fixed  by  the  requirements  of  manufacture,  the  only 
stipulation  from  an  engineering  standpoint  being  that  the  pas- 
sages must  not  be  so  small  as  to  restrict  the  flow  of  the  water 
or  steam. 

Cast-iron  radiation  is  also  furnished  in  the  form  of  "wall 
radiators"  as  illustrated  in  Fig.  22.     This  type  of  radiation  is  so 


FIG.  22. — Wall  radiator. 

proportioned  that  it  takes  up  very  little  lateral  space  and  is 
intended  to  be  hung  from  brackets.  It  is  well  adapted  for  use 
in  factory  buildings. 

The  rated  external  surface  of  radiators  of  various  widths  and 
heights  is  given  in  Table  XII  in  square  feet  of  surface  per  section. 

TABLE  XII. — HEATING  SURFACE  PER  SECTION — CAST-IRON  RADIATION 


Height, 
inches 

One- 
column 

Two- 
column 

Three- 
column 

Four- 
column 

Six-column  or 
"window"  pattern 

45 

5 

6 

10 

38 

3 

4 

5 

8 

32 

w 

3M 

43^ 

6^ 

26 

2 

2% 

m 

5 

23 

1% 

2^ 

. 

. 

'22 

.  .  . 

2M 

3 

4 

20 

1H 

2 

5 

18 

.  .  . 

2^ 

3 

.  .  . 

16 

.  .  . 

.  .  . 

m 

15 

IK 

.  .  . 

.  .  . 

14 

.  .  . 

.  .  . 

13 

3 

RADIATORS  65 

WALL  RADIATORS 

Size  of  section,  Heating  surface, 

inches  (approx.)  square  feet 

14  by  16  5 

14  by  22  7 

14  by  29  9 

It  should  be  noted  that  the  height  of  a  radiator  is  taken  as  the 
total  height  above  the  floor  for  radiators  having  legs  of  standard 
height.  The  rated  surface  given  in  the  table  does  not  corre- 
spond exactly  with  the  actual  surface,  but  the  difference  may 
be  neglected  as  the  heat  transmission  from  radiators  is  usually 
given  in  terms  of  rated  surface. 

56.  Radiator  Tappings. — The  end  sections  of  cast-iron  radia- 
tors are  usually  tapped  for  a  2-inch  pipe  thread  and  furnished 
with  bushings  having  openings  whose  size  depends  on  the  size  of 
the  radiator.     The  sizes  of  the  reduced  openings  for  radiators 
intended  for  use  with  different  systems  of  piping  are  as  follows : 

TABLE  XIII. — RADIATOR  TAPPINGS 
Single-pipe  Work 

Size  of  radiator,  Pipe  size  of  tapping, 

square  feet  inches 

Up  to  24  1 

24  to  60  IK 

60  to  100  IK 

Above  100  2 

Two-pipe  work 

Supply  Return 

Up  to  48  1  % 

48  to  96  IK  1 

Above  96  IK  IK 

Water  radiators 

Supply  Return 

Up  to  40                                       1  1 

40  to  72                                      IK  IK 

Above  72                                  1>'2  IK 
For  vapor  systems  supply,  %  inch,  return,  K  inch.     Air  valve  tapping, 
K  inch  on  all  radiators. 

57.  Pressed-metal    Radiators. — In    recent    years    radiators 
made  of  pressed  metal  have  been  introduced  and  are  now  some- 
times used.     Figure  23  illustrates  the  appearance  of  one  design  of 
this  form  of  radiator,  and  Fig.  24  is  a  cross-section.     The  sections 
are  made  of  two  sheets  of  metal  pressed  to  shape  and  welded  at 
the   edges.     In  other  designs  the  joint  is  a  lapped  seam.     A 


66 


HEATING  AND  VENTILATION 


special  alloy  or  soft  steel  selected  for  its  non-corroding  qualities 
is  used.  The  radiator  is  assembled  by  welding  the  sections 
together  or  by  joining  them  with  lapped  seams.  Pressed-metal 
radiators  are  made  in  a  variety  of  sizes  corresponding  to  those 
of  cast-iron  radiation.  The  sections  are  very  narrow  and  occupy 
much  less  space  than  do  cast-iron  radiators  of  equal  surface. 


,  Welded 


FIG.  23.— Pressed  metal 
radiator. 


FIG.  24. — Section  of  pressed 
metal  radiator. 


The  weight  per  square  foot  of  surface  is  also  much  less  than  that 
of  cast-iron  radiation,  averaging  about  2  pounds.  The  cost  is 
about  the  same  as  that  of  ordinary  cast-iron  radiation.  The 
radiating  surface  of  pressed-metal  sections  of  various  heights  and 
widths  is  given  in  Table  XIV.  Because  of  its  light  weight  this 
form  of  radiation  is  especially  suitable  for  hanging  on  wall 
brackets. 

TABLE    XIV.— PRESSED-METAL    RADIATION,    SQUARE   FEET  OF  SURFACE 

PER  SECTION 


Height  of  radiator,  inches 

Width  of  section,  inches 

*H 

»x 

45 

6 

38 

3 

5. 

32 

23^ 

4/^ 

26 

2 

3% 

22 

1% 

3 

18 

\y% 

2M 

14 

l 

... 

RADIATORS 


67 


58.  Pipe  Radiation. — In  factories  and  other  industrial  build- 
ings radiators  built  of  pipe  are  often  used  and  are  a  very  satis- 
factory form  of  radiation.  These  pipe  coils  usually  consist  of 
a  pair  of  cast-iron  headers  connected  by  four  or  more  pipes  of 
either  1  inch  or  1^4  inches  diameter.  Pipe  coils  are  usually 
made  in  the  mitre  form  as  shown  in  Fig.  25.  The  vertical 
lengths  of  pipe  provide  sufficient  flexibility  to  allow  the  longer 


I 

v_s                 ..  —           us  =j 

1 

If 

1 

I 


FIG.  25.  —  Mitre  pipe  coil. 


horizontal  members  to  expand  freely.  Some  such  provision  is 
essential.  The  openings  in  one  of  the  headers  or  the  elbows  are 
tapped  with  a  left-hand  thread  so  that  the  coil  can  be  readily 
assembled.  Pipe  coils  of  the  form  shown  in  Fig.  26  are  also 
sometimes  used,  especially  in  hot-water  work. 

Radiators  were  formerly  made  of  vertical  pipes  screwed  into 
a  cast-iron  base.     This  form  of  radiation  is  little  used  at  present. 


-    IB                                      r®i 

r®i 

PJj  —  gl  n°n  

Pl^t 

'^^^'^'^^ 

FIG.  26. — Continuous  pipe  coil. 

59.  Heat  Transmission  from  Radiators. — Heat  flows  from  the 
water  or  steam  in  a  radiator  into  and  through  the  metal  wall 
and  is  transmitted  from  the  outer  surface  partly  by  radiation 
and  partly  by  convection.  The  resistance  to  heat  flow  offered 
by  the  walls  of  the  radiator  is  so  slight  that  the  temperature  of 
the  outer  surface  is  practically  the  same  as  that  of  the  water  or 
steam.  The  amount  of  heat  transmitted  per  square  foot  of 
radiating  surface  is  affected  by  several  factors,  such  as  the  tern- 


L_U. U._" 


68  HEATING  AND  VENTILATION 

perature  difference  between  the  radiating  surface  and  the  sur- 
rounding air,  the  nature  of  the  surface,  the  height  and  shape 
of  the  radiator,  and  the  location  of  the  radiator  in  the  room. 

60.  Effect  of  Shape  of  Surface.— The  form  or  shape  of  the 
radiator  has  a  marked  effect  on  the  heat  transmission,  affecting 
both  the  amount  radiated  and  that  given  off  by  convection.     A 
greater  amount  of  heat  per  square  foot  of  surface  is  given  off  by 
radiation  from  a  pipe  coil  or  a  single-column  radiator  than  from 
a  radiator  of  a  wider  pattern.     This  can  be  clearly  understood 
from  a  study  of  Fig.  27  which  represents  horizontal  cross-sections 
of  a  single-column  and  a  three-column  radiator. 

The  rays  of  heat  from  points 
on  the  single-column  radiator 
can  travel  in  nearly  any  direc- 
tion without  interruption,  while 
the  rays  emanating  from  many 
points  such  as  A,  on  the  surface 
of  the  inner  columns  of  the 
three-column  radiator,  are 
FlG  27.  largely  intercepted  by  the  other 

portions  of  the  radiator.     It  has 

been  demonstrated  experimentally  that  the  amount  of  radiant 
heat  given  off  by  a  radiator  is  very  nearly  proportional  to  the 
area  of  the  enclosing  envelope  of  the  radiator,  as  indicated  in 
the  figure. 

The  transmission  of  heat  by  convection  is  dependent  upon  the 
difference  in  temperature  between  the  surface  of  the  radiator 
and  the  air.  The  upper  part  of  a  radiator  will  transmit  less  heat 
per  square  foot  by  convection  than  will  the  lower  part  because 
of  the  increase  in  the  temperature  of  the  air  as  it  ascends  along 
the  surface.  Hence  the  average  heat  transmission  per  square 
foot  is  greater  for  short  than  for  tall  radiators,  and  for  the  same 
reason  a  radiator  or  pipe  coil  laid  on  its  side  will  give  off  more 
heat  than  when  in  a  vertical  position. 

61.  Effect  of  Varying  Width. — Figure  28  shows  the  relative 
amount  of  heat  given  off  by  radiators  of  various  widths — that  is, 
having  one,  two,  three,  etc.,  columns.     The  narrower  radiators 
are  the  more  effective  because  of  the  reasons  explained  in  Par.  68. 

62.  Effect  of  Varying  Length. — The  effect  on  heat  transmission 
of  increasing  the  length  of  the  radiator  is  shown  in  Fig.  29. 
An  increase  of  length  has  a  marked  effect  when  the  radiator  is 


RADIATORS 


69 


under  6  sections  in  length,  but  above  10  sections,  the  effect  of 
varying  length  can  be  neglected.     The  reason  for  this  is  that  in 


ISO       200 


300 


240          2CO         2SO          300         320         340 
B.T.D. Transmitted  per  Sq. Ft. per  Hour 

FIG.  28. — Heat  transmission  from  radiators  of  various  widths. 

the  short  radiators  the  effect  of  the  ends  is  much  more  apparent 
than  in  the  long  radiators.     The  effect  of  the  end  is  to  increase 

..4CO 


0      1      2      3      45      G      7      8      9     10    11    12    13    14    15    1C    17    18    19     20 
Length  of  Radiator  in  Sectioni 

FIG.  29. — Heat  transmission  from  radiators  of  various  lengths. 

the  radiating  surface  in  proportion  to  the  convecting  surface  so 
that  in  a  short  radiator  we  get  a  larger  proportion  of  radiant 
heat  than  in  the  long  radiator.  Curves  are  plotted  for  only 


70  HEATING  AND  VENTILATION 

two  heights  of  radiator,  as  the  relative  effect  of  length  remains 
practically  the  same  in  radiators  of  different  heights. 

A  radiator  may  also  be  lengthened  by  increasing  the  spacing. 
A  few  experiments  are  available  which  show  the  effect  of  spacing. 
If  the  spacing  of  the  standard  two-column,  38~in.  radiator  is 
changed  from  2J£  in.  to  3  in.  the  results  show  that  the  heat  loss 
is  increased  about  7  per  cent.  The  hospital  type  of  radiator 
is  usually  spaced  %  in.  more  than  the  standard  type,  so  the 
hospital  type  may  roughly  be  assumed  to  give  off  from  7  to  10 
per  cent,  more  heat  than  the  standard  type. 

63.  Effect  of  Painting. — The  effect  of  painting  was  originally 
determined  by  experiments  made  with  a  cast  iron  rectangle,  and 
in  applying  these  to  radiators  of  standard  type,  corrections  must 
be  made  to  allow  for  the  difference  between  the  area  of  the  radiat- 
ing and  convecting  surfaces.  The  effect  of  painting  is  to  change 
the  radiation  constant  of  the  radiating  surface  and  has  practically 
no  effect  upon  the  heat  lost  by  convection.  It  is,  therefore,  a 
surface  effect  and  it  makes  no  difference  what  paints  are  placed 
on  the  radiator  as  a  priming  coat.  The  results  are  always 
dependent  upon  the  last  coat  of  paint  put  upon  the  radiator.  In 
radiators  having  a  large  proportion  of  radiating  surface  such  as 
pipe  coils  or  wall  coils,  the  effect  of  painting  will  be  more  marked 
than  in  four-column  radiators  having  a  comparatively  small 
radiating  surface  in  proportion  to  convecting  surface.  All  finely 
ground  materials  have  about  the  same  radiation  constant. 
Therefore  all  paints  having  finely  ground  pigments  will  give  about 
the  same  effect.  Metals  have  a  poor  radiating  effect  so*  that  any 
paint  involving  flake  metal,  such  as  bronze,  will  have  a  low 
radiating  constant.  The  following  table  shows  the  heat  loss  from 
a  two-column,  38-in.  radiator,  10  sections  long,  when  painted  with 
different  kinds  of  paints. 

TABLE  XV. — EFFECT  OF  PAINTING    ON    TWO-COLUMN    38-iN.    RADIATOR, 
STEAM  TEMPERATURE  215°.    ROOM  TEMPERATURE  70°F. 

B.t.u.  per 

square -foot 
Condition  or  surface  per  hour 

Cast  iron  bare 240 

Painted  with  aluminum  bronze 200 

Painted  with  gold  bronze 205 

Painted  with  white  enamel 242 

Painted  with  maroon  japan 240 

Painted  with  white  zinc  paint 242 

Painted  with  no-lustre  green  enamel 230 


RADIATORS 


71 


64.  Effect  of  Enclosing  the  Radiator. — It  is  very  often  desirable 
to  partly  enclose  or  conceal  a  radiator  by  means  of  screens  or 
grilles.  All  such  enclosures  in  general  reduce  the  heat  trans- 
mission from  the  radiator,  the  effect  being  usually  to  reduce  both 
the  radiant  heat  and  the  convected  heat.  As  in  most  radiators 
at  least  two-thirds  of  the  heat  is  transmitted  by  convection,  these 
enclosures  or  screens  largely  affect  the  amount  of  convected  heat. 
It  is  therefore  very  desirable  that  the  current  of  air  passing  over 
and  through  the  radiator  should  be  restricted  as  little  as  possible. 
There  has  been  some  experimental  work  done,  particularly 
abroad,  with  reference  to  these  screens.  There  are,  however,  so 
many  different  cases  that  may  arise  that  it  will  not  be  possible  to 
discuss  all  of  them  but  only  to  take  up  typical  ones. 


[cT 

I 

2ii 

IT- 

-2\ 

\ 

~IO 

i 

zz^zzztzz^ 

FIG.  31. 

21] 


FIG.  30. 

Case  No.  1. — In  this  case,  Fig.  30,  the  radiator  is  enclosed  in  a 
box  with  a  screen  in  front  at  the  bottom,  and  a  screen  at  the  top, 
these  screens  extending  the  full  length  of  the  radiator.  This  ar- 
rangement reduces  the  heat  transmission  of  the  radiator  from  7  to 
10  per  cent,  and  in  all  cases,  the  spaces  between  the  radiator  and 
the  wall  and  the  spaces  between  the  casing  and  the  radiator  should 
be  at  least  2%  inches.  The  reduction  of  heat  transmission  will  be 
more  in  narrow  radiators  than  in  wide  radiators.  Experiments 
show  that  the  best  results  are  obtained  when  the  opening  at  the 
top  has  twice  the  width  of  the  opening  at  the  bottom,  and  for 
radiators  of  ordinary  type  the  width  of  opening  at  the  bottom 
should  be  5  in.  and  the  opening  at  the  top,  10  in. 

Case  No.  2. — It  is  sometimes  desirable  to  place  a  screen  in  front 
of  the  radiator,  leaving  the  top  entirely  open  with  an  opening  at 
the  bottom  in  front  for  the  cold  air  to  enter  the  radiator,  as 
in  Fig.  31. 


72 


HEATING  AND  VENTILATION 


In  a  case  of  this  kind  the  effect  of  the  screen  is  to  produce  a 
strong  current  of  air  and  if  this  screen  is  high  enough  it  may  even 
produce  a  chimney  effect  which  will  increase  heat  transmission 
from  the  radiator  due  to  increased  circulation.  The  effect  of 
such  screens  depends  entirely  upon  their  height. 

Case  No.  3. — Radiators  often  have  placed  over  them  a  flat  shelf, 
as  shown  in  Fig.  38.  In  such  cases,  they  should  be  provided  with  a 
deflector  as  shown.  The  effect  of  the  shelf  very  largely  depends 
upon  the  height  of  the  shelf  above  the  radiator.  When  the  dis- 
tance D — that  is  the  height  of  the  shelf  above  the  radiator — is 
5  in.  or  over,  the  effect  of  the  shelf  may  be  neglected.  When  the 
distance  D  is  reduced  to  4  in.,  the  heat  effect  may  be  reduced  by 
4  per  cent. 


A 


' 


FIG.  33. 


FIG.  34. 


FIG.  35. 


Case  No.  4. — Radiators  are  often  enclosed  in  boxes  with  a  grille 
in  front  or  recessed  in  the  wall  with  a  grille  placed  in  front  of  them 
as  in  Fig.  33.  In  such  cases,  the  height,  D,  is  very  important. 
With  D  equal  to  2 %  in.,  the  heat  transmission  will  be  reduced  20 
per  cent.,  and  with  D  equal  to  6  in.,  the  heat  transmission  is  re- 
duced 10  per  cent.  It  is  assumed  in  this  case  that  the  entire  front 
of  the  box  is  provided  with  an  open  grille. 

Case  No.  5. — Sometimes  a  grille,  as  shown  in  Case  4,  is  partly 
replaced  by  a  solid  panel  with  openings  above  and  below  as  in  Fig. 
34.  With  the  openings  the  full  length  of  the  radiator  and  6  in.  in 
height  and  with  D  not  less  than  4  in.,  the  heat  transmission  will  be 
reduced  25  per  cent.  As  D  is  reduced  in  height,  the  heat  transmis- 
sion will  also  be  reduced  and  with  D  =  2%  in.,  the  reduction  will  be 
40  per  cent. 

Case  No.  6. — Radiators  are  of  ten  placed  under  seats  as  in  Fig.  35. 
In  this  case  the  distance  between  the  top  of  the  radiator  and  the 


RADIATORS  73 

bottom  of  the  seat  becomes  very  important  and  should  be  not  less 
than  3  in.  and  if  possible  it  should  be  made  6  in.  Under  favorable 
conditions,  when  D  is  at  least  3  in.  and  A  is  equal  to  6  in.,  the  heat 
transmission  will  be  reduced  from  15  to  20  per  cent.  When  D  is 
small,  however,  say  2  in.,  and  A  is  reduced  to  4  in.,  this  reduction 
may  be  35  or  40  per  cent. 

In  tests1  by  Prof.  K.  Brabbee  will  be  found  other  cases  than 
those  cited  above. 

65.  Theoretical  Formula  for  Heat  Emission. — We  have  seen 
that  heat  is  given  off  from  a  radiator  partly  by  radiation  and 
partly  by  convection.  In  developing  an  expression  for  heat 
emission  from  a  radiator,  it  will  be  necessary  to  treat  these  two 
factors  separately  as  the  laws  governing  the  two  forms  of  heat 
transmission  are  quite  different. 

We  will  start  out  with  the  assumption,  which  has  been  demon- 
strated experimentally,  that  the  surface  radiating  heat  is  the  area 
of  an  imaginary  envelope  enclosing  the  radiator,  as  in  Fig.  27. 
This  radiating  surface  is  evidently  independent  of  the  rated  sur- 
face of  the  radiator. 

The  radiant  heat  emitted  by  a  radiator,  according  to  the  law 
of  Stefan  and  Boltzman,  is  expressed  as  follows: 


in  which 

Q    =  B.t.u.  radiated  per  square  foot  of  radiating  surface  per  hour. 

Ts  =  Absolute  temperature   of  the  radiating  body,   assumed  to   be  the 

temperature  of  the  steam. 
Tr  =  Absolute  temperature  of  the  surrounding  objects,  assumed  to  be  the 

temperature  of  the  room. 
D  =  A  constant  depending  upon  the  substance  of  which  the  surface  of  the 

body  is  composed. 

The  value  of  D  for  cast  iron  radiators  may  be  taken  as  about 
0.157. 

In  order  to  express  the  heat  loss  in  terms  of  rated  surface,  let 
R  =  the  ratio  of  the  radiating  surface  to  the  rated  surface. 
Equation  (1)  then  becomes,  for  a  cast  iron  radiator  in  B.t.u.  per 
square  foot  of  rated  surface  — 


1  Reported  by  GEORGE  F.  STUMPF,  JR.  in  Heating  and  Ventilating  Magazine, 
May,  1914,  p.  23. 


74  HEATING  AND  VENTILATION 

The  convection  loss  depends  upon  the  difference  in  temperature 
between  the  air  entering  and  leaving  the  radiator,  also  upon  the 
density  and  velocity  of  the  air  passing  the  radiator. 

The  equation  for  convection  may  therefore  be  written  as 
follows : 

Q2  =  mqV(th  -  tr)  (3) 

in  which 

Qz  =  B.t.u.  lost  by  convection  per  square  foot  of  rated 

surface  per  hour. 

q  =  Density  of  the  air  passing  the  radiator. 
V  =  Velocity  of  the  air  passing  the  radiator. 
th  =  Temperature  of  air  leaving  the  radiator  (fahr.). 
tr  =  Temperature  of  air  entering  the  radiator  (fahr.). 
m  =  A  constant. 

Actual  experiments  show  that  th  bears  an  almost  constant  ratio 
to  ta,  the  temperature  of  the  steam  and  qV  also  bears  an  almost 
constant  ratio  to  t,.  We  can  therefore  write  the  expression  for 
convection : 

«2    =    C(ts    -    tr)  (4) 

in  which 

Qz  =  B.t.u.  lost  by  convection  per  square  foot  rated  surface 

per  hour. 
C  =  The  constant  for  convection  which  must  be  determined 

by  experiment. 

ta  =  Temperature  of  the  steam  in  the  radiator  (fahr.). 
tr  =  Temperature  of  the  air  in  the  room  (fahr.) . 

Adding  equation  (2),  the  heat  lost  by  radiation,  to  equation  (4), 
the  heat  lost  by  convection,  we  have  the  total  heat  lost  by  the 
radiator.  This  expression  for  total  heat  loss  becomes : 

Q  =  Qi  +  Qi  or  substituting  values. — 

-   C  (ts  -   tr)  (5) 

For  the  ordinary  forms  of  cast-iron  radiation  C  =  1  and  equa- 
tion (4)  becomes: 

Q2    =    (ts    -    tr)  (6) 

and  equation  (5)  becomes: 


RADIATORS  75 

The  value  of  R  in  equation  (7)  will  be  found  in  Table 
XVI  for  radiators  10  sections  or  more  in  length.  For  shorter 
radiators  it  should  be  computed  from  the  actual  dimension  of  the 
radiator. 

In  the  case  of  a  single  horizontal  pipe  the  value  of  R  is  1  and 
may  be  considered  a  limiting  case. 

The  use  of  the  formula  can  best  be  shown  by  assuming  an 
example  in  which  we  have  a  two-column  38  in.  radiator  of  10  sec- 
tions, steam  temperature  215  deg.,  room  temperature  70  deg. 

R  =  0.458        then: 

«-«"» -«<©'-(«)><— ™>  = 

0.072   (2075  —  784)  +  145  =  93  +  145  =  238  B.t.u.  per 
sq.  ft.  per  hour. 

The  actual  figure  taken  from  experiment  is  240  which  gives  a 
difference  of  less  than  1  per  cent  between  the  computed  and  the 
measured  results. 

66.  Radiation  and  Convection  from  Various  Types  of  Radia- 
tors.— By  means  of  equations  (2)  and  (6)  it  is  possible  to 
determine  what  proportion  of  the  total  heat  is  given  off  by 
radiation  and  by  convection. 

A  study  of  the  various  forms  of  radiators  is  given  in  Table  XVI, 
which  shows  the  proportion  of  radiant  heat  to  convected  heat  in 
the  various  types.  Radiant  heat  is  greatest  in  a  single  hori- 
zontal pipe.  The  percentage  of  convected  heat  will  be  less  in  a 
wide  radiator  such  as  the  four-column  type. 

Column  5  in  Table  XVI  shows  the  ratio  of  the  radiating  surface 
to  the  total  surface  of  the  radiator.  Column  6  shows  the  radiant 
heat  in  various  forms  of  radiators,  and  column  8  shows  the 
convected  heat.  Column  9  shows  the  ratio  of  the  convected 
heat  given  off  by  the  radiator  to  the  total  heat. 

It  will  be  noticed  that  in  the  case  of  wall  coil  about  one-half 
the  heat  is  given  off  by  radiation  and  one-half  by  convection, 
while  in  a  four-column  radiator,  about  70  per  cent  is  given  off  by 
convection  and  30  per  cent  by  radiation.  In  a  single  horizontal 
pipe  about  60  per  cent  will  be  given  off  by  radiation  and  40  per 
cent  by  convection.  It  is  apparent  from  this  table,  that  all 
radiators  do  not  give  exactly  the  same  effects  in  heating  a  room, 
and  that  the  effect  of  heating  a  room  with  pipe  coils  might  be 
called  heating  with  radiant  heat  while  heating  a  room  with 


76 


HEATING  AND  VENTILATION 


four-column  radiation  might  be  called  heating  with  convected 
heat. 

TABLE  XVI. — RELATION  BETWEEN  RADIATED  AND  CONVECTED  HEAT  IN 
DIFFERENT  TYPES  OF  RADIATORS.     10  SECTIONS  IN  LENGTH 

Room  at  70  deg.  fahr. 
Steam  at  215  deg.  fahr. 


Number 
of 
columns 

Height 
of 
radiator 

10 
Section 
rated 
surface 

10 
Section 
area  of 
enclosing 
envelope 

R 
Ratio  of 
radiating 
to  total 
surface 

Radiated 
heat  per 
sq.  ft. 
rated 
surface 

Total 
heat  per 
sq.  ft. 
rated 
surface 

Con- 
vected 
heat  per 
sq.  ft. 
rated 
surface 

Per    cent 
con- 
vected 
heat  to 
total 
heat 

One 

38 

30 

15.9 

0.53 

106 

256 

150 

58.6 

One 

32 

25 

13.5 

0.54 

108 

266 

158 

59.4 

One 

26 

20 

11.1 

0.555 

111 

273 

162 

59.4 

One 

23 

16« 

9.9 

0.595 

119 

279 

160 

57.4 

One 

20 

15 

8.75 

0.584 

117 

283 

166 

58.7 

Two 

45 

50 

21.45 

0.43 

86 

234 

148 

63 

Two 

38 

40 

18.35 

0.458 

92 

•  240 

148 

62 

Two 

32 

33  ys 

15.65 

0.47 

94 

248 

154 

62 

Two 
Two 

26 
23 

26% 
23W 

14.00 
12.70 

0.53 

0.544 

106 
109 

255 
260 

149 
151 

58 
58 

Two 

20 

20 

11.20 

0.56 

112 

265 

153 

58 

Three 

45 

60 

22.90 

0.382 

76 

218 

142 

65 

Three 

38 

50 

19.7 

0.394 

79 

226 

147 

65 

Three 

32 

45 

16.85 

0.375 

75 

233 

158 

68 

Three 

26 

37  # 

14.10 

0.376 

75 

241 

166 

69 

Three 

22 

30 

12.20 

0.407 

82 

248 

166 

67 

Three 

18 

22tf 

10.35 

0.46 

92 

254 

162 

64 

Four 

45 

100 

28.05 

0.28 

56 

205 

149 

73 

Four 

38 

80 

24.16 

0.30 

60 

210 

150 

71.5 

Four 

32 

65 

21.52 

0.331 

66 

217 

151 

69.5 

Four 

26 

50 

17.5 

0.35 

70 

225 

155 

69 

Four 

22 

40 

15.27 

0.382 

76 

232 

156 

67 

Four 

18 

30 

13.05 

0.435 

87 

238 

151 

63.5 

Wall 

5 

Coil 

Section 

5A 

13Me 

25 

21.34 

0.854 

171 

323 

152 

47 

7A 

21% 

35 

27.24 

0.78 

156 

310 

154 

49.7 

9A 

29>l6 

45 

35.32 

0.784 

157 

295 

138 

48 

In  most  cases,  heating  by  convected  heat  is  more  satisfactory 
than  heating  by  radiant  heat.  This  is  especially  true  if  the 
occupants  must  sit  in  close  proximity  to  the  radiators.  It  is 
sometimes  necessary  to  place  shields  in  front  of  the  radiators 
in  school  rooms  to  cut  down  the  radiant  heat. 

67.  Approximate  Formula. — The  foregoing  formula  checks 
closely  with  test  results  and  is  particularly  useful  because  it 
can  be  used  for  any  type  of  radiator  and  for  any  steam  or  room 
temperature.  For  a  limited  range  of  conditions,  the  following 


RADIATORS 


77 


empirical  formula  is  often  used  and  is  sufficiently  exact  for  ordi- 
nary type  of  radiators  and  ordinary  temperatures. 

H  =  SK  (ta  -  tr). 
in  which 

H  =  Heat  transmitted  per  hour. 

S  =  Rated  area  of  the  surface  of  the  radiator  in  square  feet. 

K=  Coefficient  of  heat  transmission  in  B.t.u.  per  square  foot 

per  hour  per  degree  difference  between  radiator  and 

room  temperature. 

tg  =  Temperature  of  steam  or  water  in  the  radiator. 
tr  =  Room  temperature. 

This  expression  does  not  take  into  account  the  radiant  heat 
but  assumes  that  all  of  the  heat  is  given  off  by  convection.  It 
is  therefore  applicable  only  through  a  small  range  of  temperature. 


Z.U 

1.9 

1.8 

1.7 
1.6 
1.5 
1.4 

1.3 
J 

x 

\ 

^ 

X 

\ 

^ 

^ 

-^ 

^^^ 

Column 

x 

^ 

^ 

^ 

^^ 

^ 

Column 

- 

\ 

^^ 

^"^ 

^-~ 

^^ 

Column 

"*• 

^ 

\ 

^ 

^^Z 
Column 

•^ 

^ 

^~ 

0            24             28            32            36             40            44             48 

Height  of  Radiator  -  Inches 
FIG.  36. — Coefficient  of  heat  transmission  from  radiators. 


The  values  of  K,  the  coefficient  of  heat  transmission  for 
ordinary  cast  iron  radiation  of  various  heights  and  widths,  are 
given  by  the  curves  in  Fig.  36  which  are  based  on  the  results  of 
experiments.  For  other  forms  of  radiation  the  values  of  K 
given  in  Table  XVII  may  be  taken  as  average  figures. 


78  HEATING  AND  VENTILATION 

TABLE  XVII. — COEFFICIENT  OF  HEAT  TRANSMISSION  FROM  RADIATORS 

K 

B.t.u.    per    square   foot 

per    hour    per   degree 

difference  in  temperature 

Cast  Iron,  Height  38  Inches 

One-column 1 . 75 

Two-column 1 . 65 

Three-column 1 . 55 

Four-column 1 . 45 

Wall  Coil: 

Heating  surface  5  square  feet,  long  side  vertical 1 . 92 

Heating  surface  5  square  feet,  long  side  horizontal 2.11 

Heating  surface  7  square  feet,  long  side  vertical 1 . 70 

Heating  surface  7  square  feet,  long  side  horizontal 1 . 92 

Heating  surface  9  square  feet,  long  side  vertical 1 . 77 

Heating  surface  9  square  feet,  long  side  horizontal 1 . 98 

Pipe  Coil: 

Single  horizontal  pipe 2 . 65 

Single  vertical  pipe 2 . 55 

Pipe  coil  4  pipes  high 2 . 48 

Pipe  coil  6  pipes  high 2 . 30 

Pipe  coil  9  pipes  high 2.12 

This  data  is  based  on  a  temperature  difference  between  the 
radiator  and  the  air  of  about  150°  which  represents  ordinary 
conditions.  For  other  temperatures  formula  (7),  p.  74  should 
be  used. 

68.  Heat   Transmission   from   Pressed    Metal   Radiation.— 
The  heat  transmission  from  pressed-metal  radiation  is  practically 
the  same  as  that  from  cast  iron.     This  is  illustrated  in  Fig. 
37  which  shows  the  results  of  a  test1  to  determine  the  relative 
performance  of  the  two  forms  of  radiation  under  the  same  condi- 
tions.    A  radiator  of  each  kind  was  placed  in  either  of   two 
similar  rooms  and  the  condensation  formed  in  each  radiator  was 
weighed  at  10-minute  intervals  and  the  room  temperatures  were 
measured.     While  the  rate  at  which  the  room  was  warmed  was 
nearly  the  same  in  both  cases  it  will  be  noted  that  in  the  case  of 
the  cast-iron  radiator  the  initial  condensation  of  steam  is  con- 
siderably greater. 

69.  The  Location  of  Radiators. — The  location  of  the  radiators 
in  the  room  is  extremely  important.     If  they  are  placed  along 

1  See  "Coefficient  of  Heat  Transmission  in  a  Pressed-metal  Radiator" 
by  JOHN  R.  ALLEN,  Trans.  A.  S.  H.  &  V.  E.,  1914. 


RADIATORS 


79 


an  inside  wall,  there  is  a  tendency  for  uncomfortable  drafts  to  be 
formed  by  the  cooling  effect  of  the  windows  and  outer  walls. 
The  cold  current  of  air  thus  formed  flows  without  interruption 
across  the  floor,  as  illustrated  in  Fig.  38.  This  ''window  chill" 
often  causes  extreme  discomfort,  especially  in  school  rooms, 
offices,  etc.,  and  is  best  prevented  by  placing  the  radiators 
directly  beneath  the  windows.  The  air  current  then  travels  as 


80 
40 
700 
GO 

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8   80 

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&  60 

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200 
80 

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100 

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74 
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62  | 
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Time 

FIG.  37. — Result  of  a  comparativp  test  of  a  cast  iron  and  a  pressed  iron  radiator. 

illustrated  in  Fig.  39,  the  effect  of  the  windows  being  largely 
neutralized  by  the  upward  current  of  air  from  the  radiators.  A 
secondary  circulation  is  set  up,  as  indicated,  between  the  radiator 
and  the  window.  The  location  of  the  radiators  beneath  the 
windows  is,  on  the  whole,  the  most  desirable,1  especially  in 
schools,  auditoriums,  etc.,  where  the  occupants  are  stationary. 

1  See  report  of  Committee  on  Best  Position  of  a  Radiator,  Trans.  A.S .  H  & 
V.  E.,  1916. 


80 


HEATING  AND  VENTILATION 


Recent  tests  have  indicated  that  the  transmission  of  heat  may  be 
slightly  greater  when  the  radiators  are  located  in  other  positions, 


Warm 


Cold 


* 


FIG.  38. — Effect  of  locating  radiator  away  from  window. 


FIG.  39. — Effect  of  locating  radiator  beneath  window. 

but  this  slight  gain  in  effectiveness  is  greatly  over-balanced  by 
the  other  considerations  noted  above. 


RADIATORS  81 

70.  Proportioning  Radiation. — In  designing  the  heating  system 
for  a  building  the  heat  losses  are  first  computed  and  it  is  then 
necessary  to  determine  the  amount  of  radiator  surface  which 
will  be  required  to  supply  the  heat  losses.     It  is  necessary  first 
to  know  the  temperature  of  the  steam  or  water  in  the  radiator. 
If  steam  is  the  heat-carrying  medium  the  temperature  will  be 
that  corresponding  to  the  pressure  to  be  carried.     In  many 
heating  systems  it  is  possible  to  carry  a  pressure  of  at  least  5 
pounds  when  necessary  and  for  such  systems  the  radiation  is 
commonly  figured  on  the  basis  of  this  pressure.     If,  however, 
special  conditions  require  that  a  lower  pressure  be  used,  the 
temperature  of  the  steam  which  is  assumed  should  be  that 
corresponding  to  the  pressure.     Some  types  of  vapor  heating 
systems  are  designed  to  operate  at  nearly  atmospheric  pressure, 
and  the  radiation  is  consequently  figured  for  212°.     If  hot  water 
is  used  the  temperature  will  range  between  160°  and  200°.     The 
factors  affecting  the  temperatures  carried  in  hot-water  systems 
will  be  discussed  later. 

The  type  of  radiation  and  the  height  must  next  be  selected  from 
a  consideration  of  the  nature  of  the  building  and  of  the  space 
available.  By  the  methods  given  in  the  preceding  paragraphs, 
the  heat  transmission  per  square  foot  of  surface  for  the  type  of 
radiation  selected  can  be  found  and  the  total  surface  necessary  to 
transmit  the  heat  required  can  than  be  computed.  For  example, 
consider  that  the  room  shown  in  Fig.  7,  page  23,  is  to  be  heated 
by  a  heating  system  which  is  to  operate  at  a  pressure  of  2  pounds. 
The  heat  loss  from  the  room  was  found  to  be  8696  B.t.u.  per  hour 
with  room  temperature  70°.  Assume  that  38-inch,  two-column 
radiation  is  to  be  used.  The  temperature  of  steam  at  2  pounds 
pressure  is  218.2  and  the  difference  in  temperature  between  the 
steam  and  the  air  is  218.2°  -  70°  or  148.2°.  From  the  chart  in 
Fig.  36  we,see  that  the  value  of  K  for  38-inch,  two-column  radia- 
tion is  1.65.  For  a  temperature  difference  of  148.2°  the  heat 
transmission  would  be  244  B.t.u.  per  square  foot  per  hour. 
Dividing  8696  by  this  figure  we  find  that  35.6  square  feet  of 
radiation  would  be  required.  Since  38-inch,  two-column  radia- 
tion contains  4  square  feet  of  surface  per  section,  a  radiator  of 
nine  sections  would  be  used. 

71.  Checking   a    Contractor's    Guarantee. — The    case    often 
arises  in  which  a  contractor  has  guaranteed  that  the  heating 
system  as  installed  is  capable  of  heating  the  building  to  70°  in 


82  HEATING  AND  VENTILATION 

zero  weather  and  it  is  desired  to  prove  that  this  is  true  without 
waiting  for  extremely  cold  weather.  By  means  of  the  following 
method  it  is  possible  to  determine  the  temperature  to  which  the 
building  must  be  heated  in  the  warmer  weather  if  the  heating 
system  is  capable  of  heating  it  to  the  guaranteed  temperature  in 
the  coldest  weather. 

Let  ti  =  temperature  of  outside  air  under  contract  conditions, 
t2  =  temperature  of  air  in  building  under  contract  con- 

ditions. 
fo  =  temperature  of  steam  in  radiator  at  pressure  specified. 

Test  made  with  steam  at  same  pressure. 
£4  =  temperature  of  outside  air  during  test. 
£6  =  inside   temperature   to   be  maintained   during  test 

if  system  fulfills  guarantee. 
h  =  computed  heat  loss  from  building  per  degree  dif- 

ference in  temperature. 

The  heat  loss  from  the  building  under  conditions  specified 
in  guarantee  would  be 

h(tz  -  «  (1) 

The  heat  loss  from   the   building  under  test   conditions   is 

h(t*  -  tj  (2) 

The  heat  loss  from  the  radiators  under  contract  conditions 
would  be 

K(t*  -  «  (3) 

in  which  K  is  the  coefficient  of  heat  transmission  from  the 
radiator.  The  heat  transmission  from  the  radiator  under  test 
conditions  is 

K(t>  -  tb)  (4) 

Then  the  quantity  (1)  must  be  equal  to  the  quantity  (3)  and 
the  quantity  (2)  must  be  equal  to  (4),  hence 


and 

h  - 


Equating  the  right-hand  members  of  equations  (5)  and  (6), 
we  have 


-  U 


RADIATORS 


83 


Assuming  ti  =  0°,  t2  =  70°,  and  tz  =  228°,  the  temperature 
corresponding  to  5  pounds  steam  pressure,  and  solving  for  £5 
we  have 

Z5  =  0.695*4  +  70  (8) 

The  following  table  has  been  computed  from  equation  (8)  and 
shows  the  room  temperature,  for  different  outside  temperatures 
existing  during  the  test,  which  must  be  maintained  to  fulfill 
a  guarantee  which  specifies  the  temperatures  and  steam  pressure 
given  above.  For  other  conditions  equation  (7)  must  be  solved 
for  U. 

TABLE  XVIII. — ROOM    TEMPERATURE    FOR    VARIOUS    OUTSIDE 
TEMPERATURES 


Outside  temperature 
during  test 

Room  temperature, 
two-column  radiation 

Room  temperature, 
three-column  radiation 

-30 

52.0 

53.0 

-20 

58.0 

59.0 

-10 

64.0 

64.0 

0 

70.0 

70.0 

10 

77.5 

75.0 

20 

83.0 

83.0 

30 

90.0 

89.0 

40 

97.0 

95.0 

50 

103.5 

105.5 

60 

110.0 

108.0 

70 

117.0 

115.0 

80 

123.5 

121.5 

90 

130.0 

128.0 

100 

137.0 

134.5 

72.  Indirect  Radiators. — Indirect  radiators  are  so  named  be- 
cause they  are  located  outside  of  the  room  to  be  heated  and 
the  heat  is  conveyed  from  the  radiator  to  the  room  by  a  current 
of  air.  Indirect  radiators  arfe  of  two  classes:  gravity  indirect, 
in  which  the  circulation  of  the  air  over  the  radiating  surface  is 
produced  by  the  difference  in  weight  of  the  heated  and  unheated 
columns  of  air,  and  fan  coils,  over  which  the  air  is  forced  by  a  fan. 
Only  the  former  will  be  considered  here,  the  various  types  of  fan 
systems  being  discussed  in  Chapter  XV. 

There  are  two  reasons  for  the  use  of  gravity  indirect  radiators. 
Their  chief  advantage  is  that  they  can  be  arranged  to  introduce 
fresh  air  from  outside  and  they  are  therefore  desirable  from  a 
standpoint  of  ventilation.  Another  advantage  is  that  the  radia- 


84 


HEATING  AND  VENTILATION 


tors  are  out  of  sight,  which  is  desirable  in  any  room  or  apartment 
where  appearance  is  an  important  factor.  It  is  seldom  that 
indirect  radiators  are  installed  throughout  an  entire  building 
because  of  the  increased  cost  of  installation  and  operation 
as  compared  with  direct  radiation.  In  a  residence,  indirect 
radiation  is  often  installed  in  the  living  rooms  where  ventilation 
is  most  desired  and  where  the  appearance  of  the  radiators  would 
be  objectionable,  and  direct  radiation  is  used  in  the  bedrooms, 
halls,  etc.  The  increased  operating  cost  where  indirect  radiation 
is  used  is  due  to  the  fact  that  the  large  quantities  of  air  which 
are  brought  in  from  outside  must  be  heated  up  to  room  tempera- 
ture or  above. 

73.  Forms  of  Indirect  Radiation. — As  indirect  radiators  are 
concealed,  their  appearance  is  not  an  important  factor  and  they 


FIG.  40. 


FIG.  41. 


Forms  of  indirect  radiators. 


are  therefore  designed  and  installed  from  a  standpoint  of  effec- 
tiveness rather  than  appearance.  Since  the  resistance  to  heat 
transmission  between  the  outer  surface  of  the  radiator  and  the 
air  is  greater  than  that  from  the  steam  or  water  to  the  inside 
surface  of  the  radiator  wall,  it  is  desirable  to  make  the  external 
surface  of  greater  area  than  the  internal.  This  is  accomplished 
by  adding  projections  in  the  form  of  pins  or  fins.  Two  forms  of 
indirect  radiation  are  illustrated  in  Figs.  40  and  41.  The 
sections  are  joined  together  in  the  same  manner  as  are  the 
sections  of  direct  radiators.  The  form  shown  in  Fig.  41  is  of 
the  so-called  short-pin  type.  A  similar  form  having  longer  pins 
can  also  be  obtained. 

74.  Arrangement  of  Indirect  Radiators. — Two  common  arrange- 
ments for  indirect  radiators  taking  air  from  outside  are  illus- 


RADIATORS 


85 


trated  in  Fig.  42  and  Fig.  43.  The  radiator  is  placed  in  a  chamber 
or  box  usually  situated  in  the  basement  of  the  building,  as  close 
as  possible  to  the  base  of  the  flue  leading  to  the  room  to  be 
heated.  The  air  is  admitted  to  the  radiator  chamber  by  a  duct  or 
flue  from  an  opening  in  the  outside  wall  or  from  the  room  above. 
This  duct  should  be  provided  with  a  suitable  damper,  arranged 
if  possible  to  close  when  the  steam  or  water  supply  to  the  radiator 
is  shut  off.  A  bypass  damper  should  also  be  provided,  with  a 
means  of  controlling  it  from  the  room,  so  that  the  temperature 
of  the  air  can  be  readily  adjusted. 


00000 

oooo° 


Warm  Air 


0°0°0J0°0  O  O°O°0 

0000000000 


O  000 

0000    I 


Damper 
Control 
Cable - 


Cleanout 
FIG.  42. — Indirect  radiator  with  bypass. 

The  casing  surrounding  indirect  radiators  is  usually  built 
of  galvanized  iron  and  it  should  be  bolted  together  with  stove 
bolts  so  that  the  sections  can  be  easily  removed.  A  much  better 
method  of  construction,  though  a  more  expensive  one,  is  to 
enclose  the  radiator  in  a  brick  chamber  of  sufficient  size  to 
permit  access  to  the  radiator. 

The  duct  leading  from  an  indirect  radiator  should  be  carried 
to  the  room  as  directly  as  possible.  Long  horizontal  pipes  should 
be  avoided. 

The  indirect  radiators  are  usually  suspended  in  the  box  or 
chamber  on  iron  pipes  supported  by  rods  from  the  joists.  There 
should  be  at  least  10  inches  clearance  between  the  radiator  and 
the  bottom  and  top  of  the  casing,  but  the  sides  of  the  casing 
should  fit  the  radiator  as  closely  as  possible,  so  that  all  of  the  air 


86 


HEATING  AND  VENTILATION 


must  pass  through  the  radiator.  Indirect  radiators  should  be 
placed  at  least  2  feet  above  the  water  line  of  the  boiler  if  they 
are  to  be  operated  on  a  gravity  steam  system,  and  should  be  so 


FIG.  43. — Indirect  radiator.1 

arranged  that  the  condensation  will  drain  from  them  by  gravity. 
The  tappings  of  these  radiators  are  the  same  as  for  two-pipe  direct 
steam  radiators.  The  following  table  gives  the  size  of  flues 
required  for  indirect  radiators  of  various  sizes. 

TABLE  XIX. — SIZE  OF  FLUES  FOR  INDIRECT  RADIATORS 


Heating 
surface, 
square  feet 

Area  of  cold- 
air  supply, 
square  inches 

Area  of  hot- 
air  supply, 
square  inches 

Size  of  brick 
flue  for  hot 
air,  inches 

Size  of 
register, 
inches 

20 

30 

40 

8X8 

8X8 

30 

45 

60 

8  X  12               8  X  12 

40 

60 

80 

8  X  12 

10  X  12 

50 

75 

100 

12  X  12 

10  X  15 

60 

90 

120 

12  X  12 

12  X  15 

80 

120 

160 

12  X  16 

14  X  18 

100 

150 

200 

12  X  20 

16  X  20 

120 

180 

240 

14  X  20 

16  X  24 

140 

210 

280 

16  X20 

20  X24 

iFrom  "Pipe-fitting  Charts"  by  W.  G.  SNOW. 


RADIATORS 


87 


Indirect  radiators  are  sometimes  arranged  to  re-circulate 
the  air  from  the  room  instead  of  drawing  in  fresh  air  from  out- 
side. No  ventilation  is  obtained  by  such  an  arrangement  and  the 
only  advantage  of  the  indirect  radiator  so  installed  is  that  it  is 
concealed. 

75.  Heat  Transmission  from  Indirect  Radiators. — Heat  is 
transmitted  from  indirect  radiators  almost  entirely  by  convec- 
tion. The  amount  of  heat  which  will  be  transmitted  from  a 
given  indirect  radiator  depends  upon  the  temperature  of  the 
entering  air,  the  temperature  of  the  radiator,  and  the  quantity  of 
air  passing  through  the  radiator.  The  last  quantity  depends 


FIG.  44. 

in  turn  upon  the  relative  temperatures  of  the  heated  air  and  the 
unheated  air,  and  upon  the  friction  in  the  air  ducts.  In  Fig.  44 
let  h'  be  the  average  vertical  distance  from  the  radiator  to  the 
point  of  delivery  to  the  room.  The  force  effective  in  producing 
the  flow  of  air  is  then 

p=h'(D1-D2) 
in  which  DI  =  density  of  outside  air. 

D2  =  density  of  heated  air. 

During  a  state  of  constant  flow  the  quantity  of  air  passing 
through  the  radiator  will  always  be  just  sufficient  so  that  the 
friction  loss  due  to  the  air  passing  through  the  system  will 
equal  the  available  head  producing  flow.  Owing  to  the  impossi- 
bility of  determining  in  advance  the  resistance  of  the  duct, 
because  of  lack  of  a  standard  type  of  construction,  it  is  very 


88 


HEATING  AND  VENTILATION 


difficult  to  compute  accurately  the  quantity  of  air  which  will 
pass  through  the  system.  The  action  is  also  complicated  by 
the  stack  effect  of  the  heated  room  above.  Accordingly  the 
methods  used  in  designing  indirect  radiators  are  based  on  experi- 
mental data.  Table  XX  gives  the  amount  of  heat  transmitted 
from  standard  and  long-pin  radiators  under  various  conditions. 
It  will  be  noted  that  the  temperature  to  which  the  air  is  heated 
by  the  long-pin  radiator  is  less  than  that  to  which  it  is  heated  by 
the  short-pin  radiator  with  the  same  quantity  of  air  passing. 
This  is  undoubtedly  due  to  the  fact  that  the  pins  are  so  long  that 
the  rapid  removal  of  heat  by  the  air  causes  the  ends  to  become 
cooled.  The  long-pin  type,  however,  is  very  desirable  for  use 
when  large  quantities  of  air  are  required,  as  the  air  passages  are 
ample.  This  is  the  work  for  which  it  is  primarily  designed.  The 
short-pin  type  gives  better  results  for  ordinary  residences  and 
other  buildings  where  only  small  quantities  of  air  pass  through 
the  radiator. 

TABLE    XX. — HEAT  TRANSMISSION  FROM  PIN  RADIATORS 


Cubic  feet 
of  air  passing 
per  square  foot 
of  radiation 
per  hour 

Rise  in  temperature 
of  the  air 

Pounds  of  steam 
condensed  per  square 
foot  of  radiation 

B.t.u.    transmitted    per 
square  foot  of  radiation 
per  degree  difference  in 
temperature  between 
steam  and  air 

Standard 
pin 

Long  pin 

Standard 
pin 

Long  pin 

Standard 
pin 

Long  pin 

50 

147 

140 

0.125 

0.150 

0.80 

0.95 

75 

143 

137 

0.170 

0.210 

1.17 

1.27 

100 

140 

135 

0.240 

0.260 

1.51 

1.60 

125 

138 

132 

0.295 

0.310 

1.85 

1.90 

150 

135 

129 

0.355 

0.360 

2.22 

2.20 

175 

132 

126 

0.410 

0.405 

2.57 

2.47 

200 

130 

123 

0.470 

0.450 

2.90 

2.72 

225 

127 

120 

0.530 

0.490 

3.25 

3.00 

250 

123 

118 

0.585 

0.530 

3.60 

3.20 

275 

121 

115 

0.645 

0.570 

3.90 

3.40 

300 

119 

112 

0.700 

0.610 

4.22 

3.60 

76.  Calculation  of  Indirect  Radiation. — In  order  to  determine 
the  required  size  of  an  indirect  radiator  it  is  necessary  to  assume 
the  quantity  of  air  that  will  pass  through  the  radiator.  In  school 
buildings  and  other  buildings  where  a  large  air  supply  is  desired 
and  where  the  flues  will  be  of  ample  size,  the  amount  of  air 
passing  per  square  foot  of  radiation  may  be  assumed  to  be  200 


RADIATORS  89 

cubic  feet  per  hour.  In  residences  and  buildings  where  the  flues 
are  usually  small,  the  amount  of  air  passing  per  square  foot  of 
surface  per  hour  does  not  exceed  150  cubic  feet.  The  air  should 
be  assumed  to  enter  the  radiator  at  the  minimum  outside  tem- 
perature for  which  the  system  is  to  be  designed.  If  this  tempera- 
ture is  0°,  for  example,  and  the  quantity  of  air  passing  is  taken 
as  200  cubic  feet  per  hour  per  square  foot  of  radiation,  the  air 
will  be  heated  according  to  figures  given  in  Table  XX  to  about 
130°.  The  air  which  enters  the  room  at  this  temperature  gives 
up  its  heat  to  supply  the  heat  lost  by  conduction  through  the 
walls,  and  finally  finds  its  way  out  of  the  room  through  the 
window  cracks,  foul  air  flues,  etc.  Each  cubic  foot  of  air,  there- 
fore, gives  up  enough  heat  to  lower  its  temperature  from  130° 
to  70°,  if  the  latter  is  the  room  temperature.  This  amount  of 
heat  is  equal  to 

— ~ —  X  200  =  218  B.t.u.  available  for  heating  per  square 

DO 

foot  of  radiator  surface.  This  amount  is  available  for  supply- 
ing the  heat  losses  through  the  walls  and  the  amount  of  surface 
in  the  indirect  radiator  for  the  case  given  above  would  be 
equal  to  the  computed  heat  loss  through  the  walls  divided  by  218. 
If  ventilation  requirements  made  necessary  a  greater  quantity 
of  air,  then  part  of  the  air  would  be  by-passed  around  the  radiator. 

77.  Combination  of  Direct  and  Indirect  Radiators. — A  very 
common  arrangement  is  to  install  enough  indirect  radiation  to 
give  the  proper  amount  of  air  for  ventilation  and  to  install  direct 
radiation  to  supply  the  heat  losses  from  the  walls  and  windows. 
The  direct  radiation  would  then  be  computed  in  the  ordinary 
manner,  as  if  there  were  no  other  source  of  heat.     This  system 
has  the  advantage  of  being  more  economical,  as  less  cold  air 
need  be  heated  per  hour.     Further,  when  the  rooms  are  unoc- 
cupied, the  indirect  radiators  may  be  entirely  shut  off,  resulting 
in  a  considerable  saving  of  fuel. 

78.  Semi-indirect  Radiators. — When  only  a  small  quantity  of 
air  is  needed  for  ventilation  semi-indirect  or  "flue"  radiators 
may  be  used  in  place  of  indirect  radiators.     A  radiator  of  this 
form  is  shown  in  Fig.  45.     The  air  enters  through  a  grating  in 
the  wall  behind  the  radiator  and  passes  into  a  metal  box  which 
encloses  the  lower  part  of  the  radiator  and  thence  up  through  the 
spaces  between  the  sections.     Dampers  in  the  fresh  air  opening 
and  in  the  base  may  be  adjusted  to  allow  part  or  all  of  the  air  to 


90 


HEATING  AND  VENTILATION 


re-circulate  from  the  room.  Radiators  used  for  this  purpose  are 
of  a  special  design,  the  sections  being  so  shaped  that  the  passages 
between  them  are  divided  into  a  number  of  vertical  flues.  A 
test  recently  conducted  on  a  flue  radiator  showed  that  about  45 
per  cent,  of  the  total  heat  transmitted  is  carried  off  by  the  air 


E'ecirculatiug 
Dam 


FIG.  45. — Flue  radiator. 

passing  through  the  flues,  the  remaining  55  per  cent,  being  given 
off  by  radiation  and  by  convection  from  the  outer  surfaces. 
When  flue  radiators  are  used  the  amount  of  surface  allowed 
should  be  about  25  per  cent,  greater  than  if  direct  radiation  were 
used. 

Problems 

1.  To  be  properly  heated,  a  certain  building  requires  5627  square  feet  of 
30-inch,  one-column  radiation.     How  much  would  be  required  if  wall  coil, 
of  sections  containing  9  square  feet  of  surface,  long  side  horizontal,  were 
used?     How  much  would  be  required  if  pipe  coils,  9  pipes  high,  were  used? 

2.  A  heating  system  is  guaranteed  to  heat  a  building  to  70°  in  zero 
weather  at  5  pounds  pressure.     A  test  is  made  with  the  outside  tempera- 
ture  at    10°.     What   inside   temperature   must   be   reached   to  fulfill  the 
guarantee? 


RADIATORS  91 

3.  A  heating  system  is  guaranteed  to  heat  a  building  to  65°  with  the 
outside  temperature  at  10°  and  a  steam  pressure  of  1  pound.     A  test  is 
made  with  the  outside  temperature  at  15°.     What  inside  temperature  must 
be  maintained  to  fulfill  the  guarantee? 

4.  Given  a  radiator  whose  rated  surface  is  67  square  feet.     Area  of  enclos- 
ing envelope  is  35  square  feet.     Steam  temperature  220°,  room  temperature 
68°.     What  is  the  total  heat  loss  per  hour  from  the  radiator? 

5.  Given  a  radiator  whose  enclosing  envelope  is  7  inches  wide,  30  inches  long 
and  36  inches  high.     The  radiator  consists  of  12  sections  of  38  inch  two- 
column  radiation.     Steam  temperature  190°,  room  temperature  70°.     What 
is  the  heat  transmission  per  hour  per  square  foot  of  rated  surface? 

6.  Assume  a  radiator  whose  rated  surface  is  98  square  feet.     Area  of  enclos- 
ing envelope  is  40  square  feet.     Steam  temperature  220°,  room  temperature 
70°.     What  is  the  percentage  of  the  total  heat  which  will  be  given  off  by 
convection? 

7.  Assume  that  the  room  in  Fig.  7,  p.  23,  is  to  be  heated  by  indirect 
radiation.     Inside  temperature  70°,  outside  temperature  0°.     How  much 
radiation  would  be  required  and  what  would  be  the  proper  size  for  the 
flues  and  registers? 

8.  Take  the  same  room  as  in  Prob.  7  and  figure  the  amount  of  indirect 
radiation  required  if  the  inside  temperature  is  65°  and  the  outside  tempera- 
ture 10°. 


CHAPTER  VII 
STEAM  BOILERS 

79.  Fuel. — Before  taking  up  the  subject  of  boilers,  it  is  desir- 
able to  study  the  various  kinds  of  fuel  and  the  general  principles 
of  combustion. 

Coal,  coke,  wood,  oil,  and  gas  are  used  as  boiler  fuels.  Coal 
is  by  far  the  most  widely  used  fuel  in  the  United  States,  and  is 
found  in  varying  amounts  in  no  less  than  thirty  States  in  the 
Union.  It  is  of  vegetable  origin,  being  the  remains  of  vegetation 
which  existed  during  a  former  geological  period  and  which  gradu- 
ally reached  its  present  state  through  the  action  of  decay  and  of 
earth  pressure.  The  chief  constituents  of  coal  are  carbon, 
hydrogen,  oxygen  and  nitrogen.  The  carbon  exists  partly  in  an 
uncombined  or  "  fixed, "  state  and  partly  in  combination  with  the 
hydrogen  and  oxygen  as  hydrocarbon  compounds  which  are 
given  off  as  gases  when  the  coal  is  heated.  Coals  are  classified 
as  anthracite,  bituminous,  etc.,  according  to  the  relative  pro- 
portions of  fixed  carbon  and  volatile  matter  as  given  in  Table  XXI. 

TABLE  XXI. — CLASSIFICATION  OF  COALS 


Kind  of  coal 

Composition  per  pound 
of  combustible 

Calorific 
value  per  pound 
of  combustible 
B.t.u. 

Volatile 
matter 
per  cent. 

Fixed 
carbon 
per  cent. 

Ahthracite  

3.0-  7.5 
7  .  5-12  .  5 
12.5-25.0 
25.0-40.0 
35.0-50.0 

97.0-92.5 
92.5-87.5 
87.5-75.0 
75.0-60.0 
65.0-50.0 

14,900-15,300 
15,300-15,600 
15,600-15,900 
15,800-14,800 
15,200-13,700 

Semi-anthracite  

Semi-bituminous           

Bituminous  —  Eastern           .  . 

Bituminous  —  Western  

All  coals  contain  more  or  less  non-combustible  matter,  con- 
sisting principally  of  moisture  and  ash.  The  nitrogen  in  the 
coal  is  also  a  non-combustible  but  it  is  customary  to  treat  it  as 
combustible  matter.  The  moisture  content  of  different  coals 
varies  from  2  per  cent,  to  as  much  as  20  per  cent,  and  the  ash 
content  from  4  to  20  per  cent,  by  weight  of  the  coal  as  mined. 

92 


STEAM  BOILERS 


95 


It  will  be  noted  that  the  percentages  in  Table  XX  are  base- , 
1  pound  of  combustible. 

The   bituminous   and   semi-bituminous   coals   are   the   n-    j 
abundant  and  are  the  kinds  used  for  most  industrial  purpo,  ^ 
Many  bituminous  coals  are  of  the  variety  known  as  "caki^ 
coals  because,  when  heated,  the  lumps  fuse  together  into  a  soli 
crust,  while  the  so-called  "  non-caking "  or  free-burning  coals  do 
not  possess  this  quality.     Bituminous  coals  burn  with  a  char- 
acteristic yellow  flame  and  emit  smoke  unless  burned  under 
favorable  conditions.     They  are  sold  in  the  sizes  given  in  Table 
XXII  and  as  "  run-of-mine  "  or  ungraded. 

TABLE  XXII. — COMMERCIAL  SIZES  OF  BITUMINOUS  COAL 


Kind  of  coal 

Will  pass  through 
bars  spaced 

Will  not  pass  through 
bars  spaced 

Lump                                  .        

1V£  inches 

Nut                   

\Y±  inches 

•  %  inch 

Slack                       

%  inch 

The  slack  coal  does  not  command  as  high  a  price  as  the  larger 
sizes  because  of  its  higher  ash  content  and  the  difficulty  of 
burning  it. 

Anthracite  or  hard  coal  is  principally  used  for  domestic  pur- 
poses and  for  other  conditions  where  a  smokeless  coal  is  required. 
It  ignites  slowly  but  burns  steadily  with  a  short  blue  flame.  It 
is  of  relatively  great  density  and  does  not  crumbleLe_asily.  It  is 
marketed  in  the  sizes  given  in  Table  XXIH. 

TABLE  XXIII. — COMMERCIAL  SIZES  OF  ANTHRACITE  COAL 


Kind  of  coal 

Will  pass  through 

Will  not  pass  through 

Rice 

^  -in  mesh 

3^-in  mesh 

Buckwheat  

^  -in.  mesh 

34  -in.  mesh 

Pea   .  .  . 

3^-in   mesh 

3^  -in  mesh 

Chestnut 

li^  -in  mesh 

5^-in   mesh 

Stove  or  range  

1/^-in   mesh 

1/^-in  mesh 

EEC 

2J^-in.  mesh 

1^4  -in  mesh 

Large  egg  

4-in.  mesh 

2%  -in.  mesh 

80.  Composition  and  Analysis  of  Coal. — Coal  consists  of  carbon, 
hydrogen,  sulphur,  oxygen,  and  nitrogen  combined  in  various 
ways,  together  with  moisture  and  ash.  The  moisture  includes 


HEATING  AND  VENTILATION 

that  originally  contained  in  the  coal  and  that  acquired  dur- 

storage  and  shipment.     The  moisture  content  of  a  given  coal  is 

^rmined  by  subjecting  a  finely  powdered  sample  to  a  tempera- 

3  of  about  220°F.  for  about  1  hour  and  noting  the  loss  in  weight 

.ring  that  time.  This  method,  while  not  giving  an  absolutely 
ccurate  result,  is  the  one  universally  employed. 

The  amount  of  volatile  matter  is  determined  by  subjecting 
a  sample  of  dried  coal  to  a  high  temperature  out  of  contact  with 
air  until  there  is  no  further  loss  of  weight,  and  noting  the 
decrease  in  weight.  The  residue  left  after  distilling  off  the  volatile 
matter  consists  of  the  fixed  carbon  and  ash.  By  burning  the 
sample  in  an  uncovered  crucible  the  fixed  carbon  can  be  removed, 
leaving  the  ash. 

There  are  two  forms  of  coal  analysis — the  "  Proximate  Analy- 
sis" and  the  "Ultimate  Analysis."  The  former  consists  of  a 
determination  of  the  moisture,  volatile  matter,  fixed  carbon,  and 
ash  in  the  manner  just  described.  This  is  the  more  useful  form 
of  analysis  and  is  the  one  generally  used  by  engineers,  as  it 
serves  to  show  the  type  of  coal  and  its  more  important  charac- 
teristics. The  ultimate  analysis,  which  consists  of  a  determina- 
tion of  the  carbon,  hydrogen,  oxygen,  nitrogen,  and  sulphur,  is 
necessary  only  when  a  close  study  of  the  combustion  of  coal  is 
being  made.  In  the  proximate  analysis,  the  percentages  may 
be  reckoned  either  on  a  basis  of  dry  coal  or  coal  "as  received." 
In  the  former  case  the  moisture  content  is  given  in  addition. 

The  heat  value  or  calorific  value  of  a  fuel  is  the  amount  of  heat 
developed  by  its  combustion,  expressed  in  B.t.u.  per  pound  of 
fuel.  The  heat  value  of  coal  is  determined  by  igniting  a  sample 
of  known  weight  in  a  closed  vessel  surrounded  by  water  and 
noting  the  rise  in  temperature  of  the  water.  From  the  pre- 
viously determined  thermal  capacity  of  the  vessel  and  water  the 
heat  developed  can  be  computed.  The  calorific  values  of  the 
various  kinds  of  coal  were  given  in  Table  XXI. 

81.  Cpfee. — Coke  is  the  residue  left  after  the  volatile  matter  is 
driven  off  from  bituminous  coal  and  consists  mainly  of  carbon. 
It  is jDjoduced  as  a  byproduct  in  the  manufacture  of  artificial 
gas  and  is  also  manufactured  for  various  industrial  purposes. 
Its  bulk  is  so  great  that  the  firepot  will  hold  only  a  relatively 
small  weight  of  fuel  which  is  consumed  rapidly  so  that  frequent 
firing  is  required  unless  a  very  deep  bed  of  fire  is  maintained. 

Coke  is  a  very  useful  fuel  when  a  quick,  hot  fire  is  required  or 


STEAM  BOILERS  95 

where  absolute  smokelessness  is  needed.     It  is  coming  into  wider 
use  as  a  household  fuel,  particularly  in  the  smaller  sizes. 

82.  Combustion. — Combustion  may  be  defined  as  the  chemical 
combination  of  a  substance  with  oxygen  which  proceeds  at  such 
a  rate  that  a  high  temperature  is  produced.     Carbon  is  the 
principle  combustible  in  coal.     When  its  combustion  is  complete, 
it  forms  carbon  dioxide  (CO  2) ;  when  it  is  incomplete  it  forms 
carbon  monoxide  (CO).     The  hydrogen  in  the  coal  unites  with 
oxygen  to  form  water  vapor  and  the  nitrogen,  which  is  an  inert 
substance,  -  is  set  free.     For  economy  in  fuel  consumption  it  is 
necessary  that  combustion  be  complete  and  to  this  end  the  supply 
of  air  must  be  ample.     In  order  to  insure  a  sufficient  supply  to  all 
parts  of  the  fuel  bed,  it  is  necessary  to  supply  from  150  to  300  per 
cent,  of  the  theoretical  requirements.     As  all  of  this  excess  air 
leaves  the  boiler  at  the  flue-gas  temperature,  it  is  evident  that 
in  the  interest  of  economy  this  necessary  amount  of  excess  air 
should  be  reduced  to  the  minimum.     The  best  index  of  the 
amount  of  excess  air  is  the  percentage  of  CO 2  in  the  flue  gases. 
If  exactly  enough  air  is  supplied  the  CO 2  content,  by  volume,  of 
the  flue  gases  would  be  approximately  21  per  cent.     In  practice, 
however,  the  best  results  are  obtained  with  a  CO  2  content  of 
from  10  to  15  per  cent.,  the  higher  figure  being  attainable  only 
with  mechanical  stokers.     In  th.e  ordinary  hand-fired  furnaces 
of  heating  boilers  the  CO  2  content  of  the  flue  gases  ranges  between 
13  and  5  per  cent,  which  represents  an  excess  of  air  of  from  50  to 
250  per  cent. 

Incomplete  combustion  results  when  the  air  supply  is  deficient 
or  is  incompletely  mixed  with  the  volatile  matter  which  is 
given  off  by  the  fuel.  The  presence  of  carbon  monoxide  (CO) 
in  the  flue  gases  is  an  indication  of  incomplete  combustion.  In 
the  case  of  bituminous  coal,  incomplete  combustion  is  usually 
accompanied  by  smoking. 

83.  Smoke. — Smoke  consists  principally  of  unburned  carbon  in 
finely  divided  particles  set  free  by  the  splitting  up  of  unburned 
hydrocarbon  gases.     While  the  waste  represented  by  the  visible 
products  themselves  is  not  great,  smoke  is  an  indication  of  incom- 
plete combustion  and  consequently  of  wasted  fuel.     A  great  deal 
of  damage  is  caused  by  smoke  and  in  most  communities  the 
making  of  excessive  smoke  is  prohibited  by  law. 

Smoke  may  be  avoided  by  the  use  of  anthracite  coal,  coke, 
or  the  semi-bituminous  coals,  which  have  little  volatile  matter, 


96  HEATING  AND  VENTILATION 

or  by  insuring  complete  combustion  when  coals  high  in  volatile 
matter  are  used.  When  coal  containing  much  volatile  matter  is 
placed  on  a  hot  bed  of  fuel,  the  volatile  matter  is  distilled  off. 
In  order  that  complete  combustion  of  this  gas  may  take  place, 
sufficient  air  must  be  supplied  and  intimately  mixed  with  the 
combustible  gases.  Furthermore,  the  combustion  space  must 
be  of  sufficient  size  so  that  combustion  can  be  completed  before 
the  gases  come  into  contact  with  the  relatively  cold  surfaces 
of  the  boiler.  The  air  supply  must  not  be  so  copious  or  at  such 
a  low  temperature  as  to  chill  the  mixture  below  the  temperature 
required  for  combustion.  These  requirements  are  met  by  the 
use  of  various  appliances  and  of  furnaces  of  special  design  which 
will  be  discussed  later. 

84.  Ash  and  Clinker. — Ash  is  foreign  matter  in  the  coal,  part 
of  which  is  inherent  in  the  vein  of  coal,  the  remainder  coming  from 
above  and  below  the  vein  as  it  is  mined.     Ash  is  objectionable 
because  it  reduces  the  heating  value  of  the  coal  and  because  of  the 
trouble  which  it  causes  in  the  furnace.     An  excessive  amount  of 
ash  obstructs  the  passage  of  air  through  the  fuel  bed,  causes 
clinker  formation,  and  carries  much  unburned  fuel  with  it  into 
the  refuse  pile. 

Clinker  is  simply  ash  which  has  fused  and  run  together.  When 
the  ash  has  a  low  melting  point  clinker  formation  is  most  frequent 
and  troublesome.  The  melting  point  is  thought  to  be  dependent 
upon  the  presence  of  sulphur  and  of  iron  oxides  in  the  ash. 

85.  Comparison  of  Different  Fuels. — The  following  is  a  sum- 
mary of  the  advantages  and  disadvantages  of  the  more  common 
fuels.     This  comparison  is  made  only  from  a  standpoint  of  their 
use  in  heating  boilers  and  furnaces. 

BITUMINOUS  COAL  < 

Advantages: 

Low  cost 
Disadvantages: 

Dirty  to  handle 

Difficult  to  burn  without  smoke  and  soot 

Forms  clinkers 

SEMI-BITUMINOUS  COAL 
Advantages: 

Low  cost. 

Burns  with  little  smoke 
Disadvantages : 

Dirty  to  handle 


STEAM  BOILERS  97 

ANTHRACITE  COAL 
Advantages: 

Clean  to  handle 

Burns  without  smoke 

Maintains  a  steady  fire  with  infrequent  attention 
Disadvantages: 

High  cost 

Sometimes  high  in  ash  content 

COKE 
Advantages: 

Fairly  clean  to  handle 

Burns  without  smoke 

Moderate  cost 
Disadvantages: 

Requires  frequent  firing 

Difficult  to  maintain  a  steady  fire 

Except  for  its  high  and  increasing  cost,  anthracite  coal  is 
undoubtedly  the  most  suitable  fuel  for  heating  plants  of  moderate 
size.  Its  increasing  scarcity  and  consequent  high  price  makes  the 
use  of  other  fuels  more  attractive,  however,  and  furnaces  of 
suitable  design  are  being  constantly  developed  for  burning  the 
higher  volatile  coals. 

Semi-bituminous  coals,  such  as  Pocahontas  and  New  River  are 
capable  of  being  burned  in  an  ordinary  furnace  with  little  smoke, 
though  they  are  rather  dirty  to  handle. 

The  bituminousjsoals  contain  the  greatest  heat  value  per  unit 
of  cost,  but  have  some  marked  disadvantages.  Bituminous  coal 
is  particularly  dirty  to  handle,  which  is  a  strong  argument 
against  its  use  in  residences.  It  is  also  difficult  to  burn  it  with- 
out smoke  except  in  furnaces  of  special  design,  intelligently  and 
carefully  operated.  With  the  increasing  cost  of  coal  and  growing 
scarcity  of  anthracite,  it  is  beco'ming  more  widely  used,  however, 
in  all  classes  of  work  and  many  special  furnaces  are  being  devel- 
oped for  it. 

86.  Boilers. — Strictly  speaking,  a  boiler  is  a  vessel  in  which 
steam  is  generated  by  the  application  of  heat.  The  furnace 
in  which  the  heat  is  developed  is  often  practically  an  integral 
part  of  the  boiler,  however,  and  the  term  " boiler"  therefore  often 
refers  to  the  combination  of  boiler  and  furnace.  The  primary 
requirement  in  a  boiler  is  that  it  be  of  sufficient  strength  to 
withstand  the  pressure  which  is  to  be  carried  in  it.  In  boilers 
used  for  heating  purposes  only,  this  is  comparatively  simple 


98  HEATING  AND  VENTILATION 

*^\  / 

as  the  pressure  carried  rarely  exceeds  10  pounds.  Secondly, 
the  heating  surface  must  be  sufficient  in  proportion  to  the  grat$ 
surface  so  that  the  heat  will  be  largely  removed  from  the  flue 
gases  before  they  leave  the  boiler;  and  the^ boiler  should  be  so 
designed  that  the  flue  gases  are  made  to  impinge  upon  and  rub 
along  the  heating  surfaces  to  the  greatest  possible  extent  as  this 
action  increases  the  rate  of  heat  transfer.  The  boiler  must  be  so 
designed  that  the  water  may  circulate  freely  to  the  heating  sur- 
faces and  the  steam  pass  away  from  them  withouit  restriction, 
Also,  the  area  of  the  surface  of  the  water  must  be  sufficient  so 
that  the  bubbles  of  steam  rising  through  the  water  can  escape 
without  excessively  disturbing  the  water  level^  If  the  liberating 
surface  is  restricted  or  if  the  steam  space  is  too  s'mall,  there  is  a 
tendency  for  priming  (i.e.,  the  carrying  of  water  into  the  steam 
pipes)  to  take  place,  particularly  when  the  boiler  is  being  forced. 
This  consideration  is  more  important  in  a  low-pressure  boiler  than 
in  a  high-pressure  boiler  as  the  bubbles  of  steam  have  a  greater 
volume  at  the  lower  pressure.  In  boilers  used  for  heating  pur- 
poses, it  is  desirable  to  have  a  large  storage  of  water  so  that  steam 
will  be  continuously  generated  in  spite  of  slight  variations  in  the 
condition  of  the  fire.  A  very  large  volume  of  water  is  not  desir- 
able, however,  when  the  boiler  is  operated  intermittently  as  the 
entire  mass  of  water  must  be  heated  whenever  the  boiler  is  put 
into  service. 

87.  Types  of  Boilers. — The  most  common  type  of  boiler  for 
heating  residences  and  small  buildings  is  the  round  cast-iron 
boiler  shown  in  Fig.  46.  This  type  of  boiler  consists  of  from 
three  to  five  main  castings  such  as  A.  B,  and  C  (Fig.  46).  The 
castings  are  joined  by  the  tapered  nipples  N,  N,  and  are  drawn 
and  held  together  by  vertical  bolts.  For  a  boiler  of  a  given 
diameter,  the  amount  of  heating  surface  can  be  varied  by  the  size 
or  number  of  the  intermediate  sections  such  as  B  in  the  figure. 
Naturally  the  taller  boilers  are  somewhat  the  more  efficient  since 
the  ratio  of  heating  surface  to  grate  area  is  the  greater.  Round 
boilers  may  be  obtained  having  rated  capacities  up  to  about  1600 
square  feet  of  radiation. 

The  " sectional"  boiler,  as  shown  in  Fig.  47  is  obtainable  in 
rated  capacity. up  to  about  18,000  square  feet  of  radiation.  It 
consists  of  from  five* -to  ten  sections  joined  with  nipples.  In  the 
larger  sizes  the  sections  are  made  in  halves,  the  idea  being  to 
make  the  boiler  capable  of  being  easily  transported  and  erected. 


STEAM  BOILERS 


99 


One  of  the  advantages  of  sectional  boilers  is  the  possibility  of 
erecting  them  in  an  existing  building  without  the  necessity  of 
cutting  holes  in  the  floor  or  walls. 


C 


FIG.  46. — Round  cast-iron  boiler. 


FIG.  47. — Sectional  cast-iron  boiler. 


Steel  boilers  are  freoluently  used  for  heating,  particularly  in 
large  buildings.  A  common  type  is  the  return-tubular  boiler 
illustrated  in  Fig.  48.  The  return-tubular  boiler  (so  named 


D,amper 


FIG.  48. — Horizontal  return-tubular  boiler. 

because  the  gases  flow  through  the  flues  toward  the  front  of  the 
boiler)  is  desirable  for  heating  purposes  because  of  its  large 
water  storage,  ample  circulating  areas,  and  large  liberating 


100 


HEATING  AND  VENTILATION 


surface.     Another  type  of  horizontal  fire-tube  boiler  is  the  firebox 
boiler  shown  in  Fig.  49.     Boilers  of  this  type  in  which  the  furnace 


FIG.  49. — Firebox  boiler. 


is  incorporated  with  the  boiler  are  known  as  portable  boilers  as 
distinguished  from  brick-set  boilers  of  which  that  in  Fig.  48  is  an 
example. 


Uptake 


FIG.  50. — Marine-type  boiler. 

Steel  boilers  of  the  return-tubular  and  firebox  types  are  suitable 
for  working  pressures  up  to  100  pounds.  The  marine-type 
boiler  shown  in  Fig.  50  can  be  used  for  higher  pressures  as  the 


STEAM  BOILERS 


101 


fire  does  not  touch  the  outer  shell.  Water-tube  boilers,  in  which 
the  water  circulates  through  the  tubes  and  the  flue  gases  over  the 
outside  of  them,  are  used  for  capacities  of  over  150  horsepower 
and  for  high-pressure  work. 

88.  Grates. — For  heating  boilers  the  grates  are  usually  of  the 
shaking  type,  consisting  of  a  number  of  toothed  bars  as  shown 
in  Fig.  51,  having  a  bear- 
ing at  either  end  and  con- 
nected to  a  rocking  link. 
The  free  area  through  the 
grate  is  about  50  per  cent. 


of  the  gross  area  and  the 


FIG.  51. — Shaking  grate  bar. 


width  of  the  openings  varies  from  %g  to  J£  inch,  depending 
upon  the  size  of  fuel  to  be  used.  In_  large  steel  boilers  the  grates 
are  often  stationary  and  the  ashes  are  removed  through  the  firing 
door. 

89.  The  Downdraft  Boiler. — Owing  to  the  difficulty  of  burning 
bituminous  coal  without  smoke  in  the  ordinary  boiler,  many 
boilers  have  been  designed  with  special  furnaces  for  this  purpose, 


FIG.  52. — Sectional  downdraft  boiler. 


chief  among  which  is  the  downdraft  boiler  illustrated  in  Fig.  52. 
The  furnace  consists  of  two  separate  grates  placed  one  above  the 
other.  Coal  is  fed  to  the  upper  grate  only  and  the..air,. instead  of 
passing  upward  through  the  fuel  bed  as  in  the  ordinary  furnace, 
enters  at  the  top  and  passes  downward  through  it.  Combustion 


102  HEATING  AND  VENTILATION 

is  most  actiye  at  the  bottom  of  the  fuel  bed,  and  to  prevent  the 
grate  from  being  burned  out,  it  is  made  of  hollow  bars  through 
which  the  water  in  the  boiler  circulates.  The  volatile  matter  is 
freed  from  the  coal  on  the  top  of  the  fuel  bed  and  passes  down 
through  the  incandescent  fuel  where  most  of  ru'is  ignited.  The 
lower  grate  contains  an  incandescent  fuel  bed  consisting  of 
small  pieces  of  coke  from  which  the  gases  have  been  driven  and 
which  have  fallen  down  through  the  bars  of  the  upper  grate.  In 
the  hot  combustion  chamber  between  the  grates  the  gases  descend- 
ing from  the  upper  fuel  bed  mingle  with  the  hot  air  which 
enters  through  the  lower  grate  and  complete  and  smokeless  com- 
bustion takes  place. 

In  addition  to  the  important  feature  of  burning  any  grade  of 
coal  without  smoke  and  with  complete  combustion  of  the  vola- 
tile matter,,  the  downdraft  furnace  has  other  advantages.  No 
trouble  is  vexperienced^from  clinkers,  if  the  boiler  is  properly 
fired,  and  the  performance  is  uniform  as  there  are  no  cleaning 
periods  to  disturb  the  fuel  bed. 

In  firing  a  downdraft  furnace,  it  is  important  that  the  main 
fuel  bed  be  not  seriously  disturbed.  It  should  be  frequently 
sliced,  but  just  sufficiently  to  crack  the  caked  mass  of  fuel  so 
that  air  can  find  its  way  through  it.  No  green  coal  should  ever 
be  fed  to  the  lower  grate;  it  should  contain  only  such  material 
as  falls  through  from  the  upper  grate.  The  main  air  supply  of 
course  enters  through  the  firing  door  of  the  upper  grate  and  the 
fire  is  controlled  by  the  regulation  of  this  air  opening.  The  one 
great  disadvantage  of  the  downdraft  furnace  is  the  necessity  for 
fairly  careful  firing,  without  which  the  smokeless  feature  is  lost. 
If  green  coal  is  shovelled  on  the  lower  grate,  if  the  lower  grate  is 
not  properly  covered,  or  if  the  upper  fuel  bed  is  violently  dis- 
turbed by  poking,  much  smoke  will  be  formed.  Any  of  these 
things  are  very  liable  to  be  done  by  a  careless  attendant. 

90.  Other  Special  Furnaces. — Another  means  of  promoting 
the  thorough  mixing  and  combustion  of  the  air  and  volatile 
matter  necessary  for  smokelessness  is  by  the  use  of  some  form 
of  brick  ignition  arch  or  wall.  In  the  boiler  shown  in  Fig.  53  the 
gases  are  made  to  pass  from  the  fuel  bed  into  the  " mixing" 
chamber  and  thence  through  the  vertical  slot  in  the  ignition  wall 
to  the  combustion  chamber.  The  ignition  wall  becomes  highly 
heated  and  serves  to  assist  in  the  ignition  of  the  gases,  the  narrow 
slot  causing  a  thorough  intermingling  of  the  gases  and  air.  The 


STEAM  BOILERS 


103 


air  supply  enters  principally  through  the  fuel  bed  and  an  auxiliary 
air  suppry^is  provided  above  the  fuel  bed. 

With  a  boiler  of  this  type,  some  smoke  is  unavoidable  during 
the  firing  periods  when  the  doors  are  open,  admitting  great  vol- 
umes of  cold  air  and  when  the  green  coal  thrown  upon  the  fire 
is  giving  off  a  large  amount  of  hydrocarbon  gases.  For  the 
greater  part  of  the  time,  however,  smokeless  combustion  is 
obtained. 

Another  type  of  smokeless  boiler  which  is  coming  into  wider  use 
employs  a  secondary  air  supply  which  is  preheated  and  mixed 


Ignition. 
Wall 


\ 
Mixing  Chamber 

~— »3>- — " 

FIG.  53. — Smokeless  boiler  with  brick  ignition  wall. 

with  the  combustible  gases  at  the  proper  point  in  their  path, 
thus  promoting  complete  combustion. 

Other  devices  for  the  prevention  of  smoke  consist  of  ignition 
arches  of  various  designs,  and  of  steam  jets  directed  into  the 
furnace  so  as  to  cause  a  thorough  mixing  of  the  air  and  gases. 

An  interesting  type  of  special  boiler  is  the  magazine-feed  type 
designed  primarily  for  burning  the  small  sizes  of  anthracite  coal 
and  coke.  These  fuels  cannot  be  burned  successfully  in  an  ordi- 
nary boiler  because  of  the  difficulty  of  getting  air  through  a  fuel 
bed  of  any  considerable  thickness,  while  a  thin  fuel  bed  requires 
very  frequent  firing.  With  the  magazine-feed  such  as  illustrated 


104 


HEATING  AND  VENTILATION 


in  Fig.  54  the  fresh  fuel  is  fed  by  gravity  as  required  and  the  fuel 
bed  is  at  all  times  sufficiently  thin  to  allow  air  to  pass  through  it. 
The  magazine  holds  sufficient  fuel  so  that  the  boiler  needs  atten- 
tion only  at  much  less  frequent  intervals  than  does  the  ordinary 
boiler. 


FIG.  54. — Magazine  feed  boiler. 

91.  Proportions  of  Boilers. — The  heating  surfaces  in  a  boiler 
are  defined  as  those  surfaces  which  have  water  on  one  side  and 
hot  gases  on  the  other  side.  In  order  that  the  boiler  may  be 
efficient  the  ratio  of  heating  surface  to  grate  surface  should  be 
large.  The  ratio  is  limited  in  practice.,  however,  by  such  factors 
as  the  cost  of  the  boiler  and  the  friction  introduced  in  the  path  of 
the  flue  gases.  In  small  boilers  it  is  usual  to  allow  1  square  foot  of 
grate  surface  to  every  15  to  30  square  feet  of  heating  surface. 
For  boilers  of  50  horsepower  an>d  over,  it  is  usual  to  allow  from  30 
to  40  square  feet  of  heating  surface  per  square  foot  of  grate  sur- 
face, while  in  very  large  boilers  the  ratio  is  50  or  60  to  1.  Expe- 
rience has  shown  that  in  small  heating  boilers  it  is  advisable  to 
allow  each  square  foot  of  heating  surface  to  evaporate  only  about 
2  pounds  of  water  per  hour  as  a  greater  rate  of  steaming  results  in 
a  high  exit  temperature  of  the  flue  gases.  In  large  boilers  the 


STEAM  BOILERS  105 

evaporation  rate  varies  from  3  to  6  pounds  per  square  foot  of 
surface. 

Small  heating  boilers  are  distinctly  different  in  operation  from 
large  power  or  heating  boilers.  In  the  latter,  coal  is  being  fed 
to  the  boiler  almost  continuously  and  the  flues  are  carrying 
a  large  quantity  of  gases.  Small  heating  boilers,  on  the  other 
hand,  are  fed  with  coal  only  at  infrequent  intervals  and  very 
little  of  the  heat  is  transmitted  to  jthe  water  by  the  flue  surfaces, 
the  greater  part  of  the  heat  being  transmitted  by  the  fire  surfaces, 
i.e.,  those  which  are  in  the  paths  of  the  heat  rays  emanating 
from  the  fuel  bed.  During  the  periods  when  the  drafts  are  closed 
most  of  the  steaming  in  the  boiler  is  produced: by  the  fire  surface. 
It  is  good  practice  to  have  about  60  per  cent,  fire  surface  and  40 
per  cent,  flue  surface  in  small  cast-iron  boilers. 

92.  Boiler  Rating. — The  standard  unit_ofj3oiler  capacity  is  the 
boiler  horsepower  which  is  defined  as  the  equivalent  of  34.5 
pounds_Qf^ibeam  evaporated  "from  and  at"  212°  (i.e..  from  water 
at  212°  into  saturated  steam  at  the  same  temperature).  As  each 
pound  of  steam  so  evaporated  requires  the  transmission  of  970.4 
B.t.u.,  the  boiler  horsepower  is  equivalent  to  33,479  B.t.u.  per 
hour.  It  is  customary  to  allow  10  square  feet  of  heating  surface 
per  boiler  horsepower  for  establishing  the  rated  capacity  of  a 
boiler.  On  this  basis,  one  square  foot  of  surface  when  working  • 
a^j^ted__capacity  evaporates  3.45  pounds  of  water  per  hour. 
Large  boilers  have  an  overload  capacity  of  from  50  to  100  per  cent. 

Heating  boilers  are  not  usually  rated  in  horsepower  but  by  the 
amount  of  radiation  which  they  will  handle  or  in  B.t.u.  per  hour. 
The  radiation  ratings  are  published  by  each  manufacturer  for 
his  own  boiler  but  do  not  always  represent  the  true  capacity  of 
the  boiler,  so  that  it  is  necessary  to  use  them  with  caution  unless 
they  have  been  established  by  actual  tests. 

The  capacity  of  a  heating  boiler  depends  upon  quite  different 
factors  from  those  on  which  a  power  boiler  is  rated.  A  heating 
boiler,  unless  of  large  size,  must  run  for  several  hours  on  one 
charge  of  fuel.  The  amount  of  steam  which  it  is  capable  of 
generating  depends  upon  the  amount  of  fuel  burned  $er  hour  and 
this  is  in  turn^fixed  by  the  fuel  holding  capacity  of  the  boiler  and 
the  allowable3iength  of  the  firing  period.  The  firebox  must  be 
large  enough  to  holol  the  fuel  required  for  a  given  firing  period 
plus  at  least  20  per  cent,  excess  for  igniting  the  next  charge. 
Consequently,  a  given  boiler  may  be  driven  at  a  high  rate  with  a 


106  HEATING  AND  VENTILATION 

short  firing  interval  or  at  a  lower  rate  with  a  longer  firing  interval- 
It  is  always  necessary  to  consider  the  firing  period  when  determin- 
ing the  rating  of  a  boiler. 

The  efficiency  of  the  boiler  is  also  a  factor  in  the  output  of 
which  it  is  capable.  The  efficiency  usually  decreases  with  increas- 
ing loads,  principally  because  the  amount  of  heat  lost  in  the  flue 
gases  increases.  It  is  thus  evidently  impossible  to  determine  the 
capacity  of  a  boiler  accurately  except  by  test.  The  leading 
manufacturers  use  this  method  in  rating  their  boilers. 

The  capacity  of  a  heating  boiler  may  be  expressed  as  follows: 

Q  =  W  X  G  X  H~X  E 
in  which 

Q  =  boiler  output  in  B.t.u.  per  hour. 

W  =  weight  of  fuel  burned  per  hour  per  sq.  ft.  of  grate  area. 

G  =  grate  area,  sq.  ft. 

H  =  calorific  value  of  fuel,  B.t.u.  per  pound. 

E  =  combined  efficiency  of  boiler  and  grate. 

In  computing  the  boiler  output  necessary  for  a  given  heating 
system,  it  is  customary  to  assume  that  a  square  foot  of  direct 
steam  radiation  requires  250  B.t.u.  per.  hour  and  a  square  foot  of 
hot  water  radiation  requires  150  B.t.u.  per  hour.  To  this  must 
be  added  the  equivalent  of  the  mains  and  risers.  If  uncovered, 
such  piping  should  be  computed  as  an  equal  amount  of  radiation. 
If  insulated,  the  heat  loss  should  be  computed  according  to  the 
kind  of  covering.  Twenty-five  per  cent,  of  the  radiator  surface  is 
often  used  as  an  approximate  figure  to  represent  the  loss  from 
piping.  An  additional  factor  of  safety  to  allow  for  such  things  as 
dirty  flues,  poor  fuel,  etc.,  should  usually  be  added,  amounting  to 
from  15  to  25  per  cent.  Sometimes  it  is  desirable  to  increase 
this  factor,  in  case  the  building  must  be  heated  intermittently  and 
quickly. 

Table  XXIV1  gives  the  square  feet  of  direct  steam  radiation  per 
square  foot  of  grate  area  at  various  combustion  rates  and 
efficiencies,  based  on  anthracite  coal  having  a  calorific  value  of 
12,000  B.t.u.  per  pound.  For  example,  with  a  combustion  rate 
of  7  pounds  per  square  foot  per  hour,  a  boiler  operating  at  65  per 
cent,  efficiency  could  supply  201.6  square  feet  of  direct  steam 

1  From  report  of  Committee  on  Rating  of  Heating  Boilers,  Trans.  A.  S.  H.* 
&  V.  E.,  1911. 


STEAM  BOILERS 


107 


TABLE  XXIV. — RATINGS  OF  CAST-IRON  BOILERS  IN  TERMS  OF  SQUARE  FEET 

OF  DIRECT  STEAM  RADIATION  PER  SQUARE  FOOT  OF  GRATE 

AREA,  WITH  DIFFERENT  RATES  OF  COMBUSTION  AND 

DIFFERENT  BOILER  EFFICIENCIES 

ASSUMPTIONS. — (a)  Coal  heat  value  =  12,000  B.t.u.  per  pound;  (6) 
boiler  efficiency  =  ratio  of  heat  given  off  beyond  nozzle  to  heat-value  of 
coal  burned;  (c)  one  square  foot  of  direct  steam  radiating  surface  gives  off 
250  B.t.u.  per  hour. 

NOTE. — All  radiating  surface  giving  off  different  amounts  of  heat  than 
250  B.t.u.  per  hour  per  square  foot  may  be  reduced  to  " equivalent  direct 
surface"  at  250  B.t.u.  per  hour  per  square  foot  for  use  in  connection  with 
this  table. 


££ 

Boiler  efficiencies 

o3  v 
ftft 

(Per  cent.) 

If 

50.0 

52.5 

55.0 

57.5 

60.0 

62.5 

65.0 

67.5 

70.0 

75.2 

75.0 

£ 

Square  feet  of  direct  radiation 

i 

24.0 

25.2 

26.4 

27.6 

28.8 

30.0 

31.2 

32.4 

33.6 

34,8 

36.0 

2 

48.0 

50.4 

52.8 

55.2 

57.6 

60.0 

62.4 

64.8 

672 

69.6 

72.0 

3 

72.0 

75.6 

79.2 

82.8 

86.4 

90.0 

93.6 

97.2 

100.8 

104.4 

108.0 

4 

96.0 

100.8 

105.6 

110.4 

115.2 

120.0 

124.8 

129.6 

134.4 

139.2 

144.0 

5 

120.0 

126.0 

132.0 

138.0 

144.0 

150.0 

156.0 

162.0 

168.0 

174.0 

180.0 

6 

144.0 

151.2 

158.4 

165.6 

172.8 

180.0 

187.2 

194.4 

201.6 

208.8 

216.0 

7 

168.0 

176.4 

184.8 

193.2 

201.6 

210.0 

218.4 

226.8 

235.2 

243.6 

252.0 

8 

192.0 

210.6 

211.2 

220.8 

230.4 

240.0 

249.6 

259.2 

268.8 

278.4 

288.0 

9 

216.0 

226.8 

237.6 

248.4 

259.2 

270.0 

280.8 

291.6 

302.4 

313.2 

324.0 

10 

240.0 

252.0 

264.0 

276.0 

288.0 

300.0 

312.0 

324.0 

336.0 

348.0 

360.0 

radiation  per  square  foot  of  grate  area.  If  the  grate  is  20 
inches  in  diameter  (area  2.18  sq.  ft.)  the  total  capacity  is  2.18  X 
201.6  =  439.5  sq.  ft. 

Heating  boilers,  using  anthracite  coal,  usually  operate  at  from 
55  to  65  per  cent,  efficiency  at  full  capacity.  The  rate  of  com- 
bustion to  be  assumed  depends  upon  the  size  of  the  boiler  and  the 
kind  of  fuel  used.  In  general,  the  larger  the  boiler,  the  higher 
the  allowable  rate  of  combustion  per  square  foot  of  grate  area. 
A  combustion  rate  of  5  to  7  pounds  per  hour  per  square  foot  is 
good  practice  for  ordinary  conditions. 

The  volume  of  the  fire  pot  must  be  sufficient  to  contain  the 
fuel  needed  for  the  firing  period  plus  a  reserve  of  approximately 
20  per  cent,  to  ignite  the  next  charge  of  fuel.  For  ordinary 
conditions,  with  small  or  medium  sized  boilers  burning  anthracite 
coal,  the  firing  period  assumed  should  be  at  least  8  hours.  For 
residences,  a  10  hour  firing  period  is  preferable.  For  larger 


108  HEATING  AND  VENTILATION 

boilers  where  frequent  or  continual  attendance  is  available,  the 
charges  of  fuel  will  naturally  be  more  frequent  and  smaller  and 
the  combustion  rate  higher.  In  the  foregoing  example,  the 
boiler  burning  7  pounds  of  coal  per  square  foot  per  hour  should 
have  a  fire  pot  large  enough  to  hold  7  (pounds)  X  2.18  (square 
feet)  X  8  (hours)  X  1.20  =  146.5  pounds  of  coal.  It  is  custom- 
ary to  use  as  the  depth  of  the  fire  pot  the  distance  from  the 
center  of  the  furnace  door  to  the  grate.  For  anthracite  coal,  the 
weight  per  cubic  foot  is  taken  as  50  pounds. 

93.  Use  of  Bituminous  Coal. — In  all  of  the  foregoing,  the  boiler 
performance  is  based  on  anthracite  coal  which  is  assumed  to 
have  a  heating  value  of  12;000  B.t.u.  per  pound.     If  bituminous 
coal  is  used,  the  firing  conditions  are  somewhat  different.     This 
fuel  requires  more  frequent  attention  for  slicing  the  fire  and  for 
charging   fuel.     The   large   quantities   of   soot   emitted    cause 
accumulations  on  the  heating  surfaces  which  reduce  the  efficiency 
and  consequently  the  capacity  of  the  boiler.     Bituminous  coal 
occupies  25  per  cent,  more  space  per  pound  than  anthracite  and 
the  size  of  the  furnace  must  be  based  on  this  volume.     The 
calorific  value  varies  considerably,  ranging  from  10,000  to  14,000 
B.t.u.  per  pound. 

Some  engineers  install  two  boilers  in  buildings  of  considerable 
size,  each  having  a  capacity  sufficient  to  take  care  of  about  two- 
thirds  of  the  maximum  load  which  could  be  expected.  This 
practice  enables  one  boiler  to  be  operated  at  an  active  rate  of 
combustion  during  the  greater  part  of  the  time  and  provides  a 
spare  boiler  sufficient  to  handle  almost  the  entire  load  if  forced. 
In  very  large  buildings  even  more  spare  capacity  should  be 
provided. 

94.  Boiler  Accessories. — Every  steam  boiler  should  be  equipped 
with   a  safety   valve   of    sufficient   capacity   to   handle   all   of 
the  steam  which  the  boiler  can  generate.     A  safety  valve  of 
the  spring-loaded  type  is  shown  in  Fig.  55.     A  safety  valve 
of  the  weight  arid  lever  type  is  undesirable  as  it  can  be  rendered  in- 
operative through  the  suspending  of  extra  weights  on  the  lever. 
The  safety  valve  should  be  piped  a  few  feet  away  from  the  boiler 
so  that  a  discharge  of  steam  from  it  will  not  injure  the  covering  of 
the  boiler.     The  valve  should  be  set  to  operate  at  from  2  to  5 
sounds  above  the  normal  pressure. 

^A  jva/ter  column  is  required  to  indicate  the  level  of  the  water  in 
the  boiler.  It  should  be  equipped  with  a  gage  glass  and  with  try- 


STEAM  BOILERS 


109 


cocks  as  shown  in  Fig.  56,  the  latter  being  desirable  for  use  in 

case  the  gage  glass  becomes  broken  or  to  verify  its  showing. 

C3>   A  steam  pressure  gage  similar  to  that  in  Fig.  57,  is  also  required. 


FIG.  55. — Safety  valve. 


FIG.  56. — Water  column. 


To  facilitate  the  control  of  the  drafts,|yid  to  maintain  an  even 
steam  pressure  some  form  of  damper  regulator  operated  by  the 
pressure  in  the  boiler  is  very  desirable.  The  form  shown  in 


FIG.  57. — Steam  pressure 
gage. 


FIG.  58. — Damper  regulator. 


Fig.  58  consists  of  a  corrugated  metal  bellows  which  expands 
under  pressure,  closing  the  ashpit  damper  and  opening  the  check 
damper  in  the  flue  by  means  of  chains  or  rods  connected  to  the 


110  HEATING  AND  VENTILATION 

lever.     The  pressure  at  which  the  action  takes  place  depends 
upon  the  location  of  the  weight  on  the  lever  arm. 

95.  Draft  and  Chimney  Construction.-t-In  order  to  maintain 
combustion  in  a  furnace  a  continuous  supply  of  air  must  be  moved 
through  the  fuel  bed.  In  the  ordinary  heating  boiler,  the  air 
is  drawn  through  by  means  of  a  chimney,  which  also  serves  to 
dispose  of  the  smoke  and  other  products  of  combustion.  The 
chimney  produces  a  " draft"  or  movement  of  the  air  because 
of  the  difference  in  weight  between  the  column  of  hot  gases  in 
the  chimney  and  the  cold  outside  air. ..  The  intensity  of  the  force 
produced  depends  upon  the  average  difference  in  temperature 
between  the  hot  gases  in  the  stack  and  the  outside  air  and  upon 
the  height  of  the  stack.  This  force  must  be  sufficient  to  move  the 
required  amount  of  air  and  gases  through  the  boiler  and  stack 
against  the  frictional  resistances  interposed  by  the  various 
obstructions.  These  resistances  consist  of  (a)  the  resistance  of 
the  fuel  bed,  (6)  the  resistance  of  the  flues  of  the  boiler,  (c)  the 
resistance  of  the  damper  and  breeching,  and  (d)  the  resistance 
of  the  stack  itself.  The  first  three  items  are  fixed  by  the  kind  of 
fuel  used  and  by  the  design  of  the  boiler.  The  last  item  depends 
upon  the  height,  cross-section,  and  construction  of  the  stack. 
If  the  cross-sectional  area  of  the  stack  is  too  small,  the  friction 
in  the  stack  itself  will  be  great  and  the  sum  of  the  various 
resistance  factors  may  be  greater  than  the  available  draft  produced 
by  the  stack.  Increasing  the  area  of  the  stack  results  in  a 
reduction  of  its  frictional  resistance  and  therefore  in  an  increase 
in  the  net  amount  of  draft  available  at  the  foot  of  the  stack  for 
overcoming  the  boiler  and  breeching  losses.  Increasing  the 
height  of  the  stack  obviously  increases  the  available  draft. 

The  dimensions  of  a  chimney  can  be  computed  from  a  consid- 
eration of  the  principles  stated  above,1  but  for  ordinary  cases 
they  can  be  determined  by  empirical  rules.  Table  XXV  gives 
the  dimensions  of  chimneys  for  various  amounts  of  steam  or 
water  radiation. 

The  available  draft  of  such  chimneys,  properly  designed  and 
constructed,  as  measured  with  an  ordinary  draft  gage,  should 
approximate  the  values  given  in  Table  XXVI. 

In  measuring  the  available  draft  the  gage  should  be  connected 
to  the  breeching  on  the  chimney  side  of  the  damper.  The  fire 
should  be  regulated  so  that  the  temperature  of  the  stack  gases 

1  For  methods  of  chimney  design  see  GEBHARDT,  "Steam  Power  Plants." 


STEAM  BOILERS 


111 


TABLE  XXV. — MINIMUM  CHIMNEY  FLUE  SIZES  FOR  BOILERS  AND  FURNACES 


Warm  air 
furnace 
capacity 
in  leader 
pipe, 
sq.  in. 

Boiler 
hot  water 
rating, 
sq.  ft. 

Capacity 
steam 
(direct) 
rating, 
sq.  ft. 

Number  of  heaters  attached  to  each  flue 

1 

2 

3 

Dimensions, 
in. 

A 

M^J 
'£<« 

w 

Dimensions, 
in. 

+a 

A 
**-tJ 

"3*4"1 
W 

Dimensions 
in. 

J3 

.5»~    • 
<D«« 

w 

To    450 

To  700 

To  450 

8  X  12 

35 

800 

900 

600 

8  X  12 

35 

1000 

1100 

700 

8  X  12 

40 

1500 

1000 

12  X  12 

35 

2500 

1500 

12  X  12 

40 

12  X  16 

45 

16  X20 

50 

4000 

2500 

12  X  16 

40 

16  X  20 

50 

20  X24 

55 

5800 

3600 

16  X  16 

45 

20  X  24 

55 

24  X  28 

60 

7300 

4500 

16  X  20 

50 

24  X  24 

60 

28  X  32 

65 

8700 

5400 

20  X  20 

55 

24  X  28 

65 

30  X  30 

70 

10,000 

6400 

20  X  24 

60 

28  X  28   | 

70 

30  X32 

80 

12,000 

7400 

24  X  24 

65 

30  X  30      75 

32  X  32 

85 

14,000 

8400 

24  X  28 

65 

32  X  32 

75 

30  X36 

85 

15,000 

9400 

28  X  28 

70 

30  X  36 

80 

36  X36 

90 

17,000 

10,400 

28  X  32 

70 

30  X  36 

80 

36  X42 

90 

19,000 

11,400 

30  X  30 

70 

36  X36 

80 

42  X42 

90 

NOTE:  Where  round  tile  is  used  in  place  of  rectangular  tile,  the  nearest 
corresponding  size  shall  be  used. 

TABLE  XXVI. — DRAFT  IN  SMALL  CHIMNEYS* 


Height  in  feet 


200 


Temperature  of  chimney  gases,  deg.  F. 
250 


300 


Draft  —  inches  of  water 

I 

60 

0.27 

0.32 

0.35 

55 

0.25 

0.29 

0.32 

50 

0.23 

0.26 

0.29 

45 

0.21 

0.23 

0.26 

40 

0.18 

0.21 

0.23 

35 

0.16 

0.19 

0.20 

30 

0.14 

0.16 

0.17 

25 

0.12 

0.14 

0.14 

20 

0.09 

0.11 

0.1$ 

will  approximate  working  conditions  and  the  damper  should  be 
quickly  closed  immediately  before  the  reading  is  taken. 

A  chimney  must  be  so  constructed  that  the  wind,  deflected  by 
surrounding  buildings,  will  not  blow  down  into  it  and  thus 

1  From  "Chimneys:  Their  Design  and  Construction,"  by  HAROLD  L.  ALT, 
Heating  &  Ventilating  Magazine,  March,  1917. 


112  HEATING  AND  VENTILATION 

impede  the  draft.  The  chimney  should  be  extended  well  above 
the  top  of  all  adjacent  buildings. 

The  round  flue  is  the  most  effective  per  square  foot  of  area 
but  is  somewhat  difficult  to  construct.  For^small  buildings  a 
square  or  rectangular  flue  is  used.  It  shoula  be  lin§d  with  tile 
and  should  be  smooth 'and  free  from  leaks.  Offsets  should 
always  be  avoided)  if  possible,  and  when  unavoidable  should 
be  made  with  gradual  bends.  No  other  openings  (except  a 
clean-out  door)  should  be  made  in  the  flue  to  which  the  boiler  is 
connected. 

In  large  buildings  the  stack  is  often  constructed  of  steel, 
lined  with  brick  or  tile. 

96.  Hot-water  Heaters. — For  hot-water  systems  the  heater 
used  is  very  similar  to  the  steam  boiler.  In  cast-iron  water 
heaters  of  both  the  round  and  sectional  type  a  smaller  casting  is 
substituted  for  the  steam  dome.  For  large  buildings  ordinary 
steel  boilers  are  often  used,  although  in  many  cases  the  water  is 
heated  by  the  exhaust  steam  from  generating  units  in  some  form 
of  "  surf  ace"  heater. 

The  water  column,  safety  valve,  and  pressure  gage  are  of  course 
omitted  from  a  water  heater. 

Problems 

1.  A  boiler  evaporates  1,749  pounds  of  water  per  hour  from  a  tempera- 
ture of  180°  into  steam  at  10  pounds  gage  pressure  and  98  per  cent,  quality. 
What  is  the  equivalent  evaporation  "from  and  at"  212°,  and  what  boiler 
horsepower  is  developed? 

2.  A  boiler  containing  820  square  feet  of  heating  surface  evaporates  2600 
pounds  of  water  per  hour,  from  a  temperature  of  190°  into  steam  at  50 
pounds  gage  pressure  and  97  per  cent,  quality.     What  per  cent,  of  rating 
is  developed? 

3.  A  heating  system  contains  4,210  square  feet  of  steam  radiation.     What 
should  be  the  grate  area  of  the  boiler,  assuming  an  efficiency  of  60  per  cent, 
and  a  combustion  rate  of  6  pounds  of  anthracite  coal  per  square  foot  per  hour? 
What  should  be  the  volume  of  the  fire  pot  for  an  8-hour  firing  period? 

4.  A  building  contains  3,657  square  foot  of  steam  radiation.     The  piping 
is  covered  with  an  insulator  which  allows  a  heat  loss  of  75  B.t.u.  per  square 
foot  of  pipe  surface  per  hour  and  there  are  1,500  square  feet  of  pipe  surface. 
What  should  be  the  grate  area  of  the  boiler,  assuming  a  combustion  rate  of 
6  pounds  per  square  foot  per  hour  and  65  per  cent,  efficiency? 

5.  A  building  contains  4,000  square  feet  of  hot  water  radiation  including 
the  equivalent  for  the  piping.     What  should  be  the  grate  area  of  the  heater 
at  a  combustion  rate  of  6  pounds  per  square  foot  per  hour  and  an  efficiency 
of  65  per  cent? 

s 


CHAPTER  VIII 
STEAM  HEATING  SYSTEMS 

97.  Classification  of  Systems. — In  a  steam  heating  system  the 
piping  and  radiators  must  be  arranged  with  a  view  to  perform- 
ing successfully  three  functions:  (1)  the  conveying  of  steam  to  the 
radiators,  (2)  the  removal  of  air  from  the  radiators,  and  (3)  the 
draining  off  of  the  condensation  from  the  radiators.     The  many 
types  of  steam  heating  systems  in  use  differ  from  one  another 
mainly  in  the  manner  in  which  these  operations  are  accomplished. 
It  is  the  purpose  of  this  chapter  to  discuss  these  various  types 
and  their  relative  merits  for  different  classes  of  buildings. 

Steam  heating  systems  may  be  divided  roughly  into  two  gen- 
eral classes  according  to  the  manner  in  which  the  connections 
are  made  to  the  radiators.  In  the  single-pipe  systems  the  steam 
is  conveyed  to  the  radiator  through  a  pipe  which  enters  the 
radiator  at  the  bottom  of  one  of  the  end  sections.  The  con- 
densation which  forms  in  the  radiator  flows  back  through  this 
same  pipe.  In  the  two-pipe  systems  a  separate  system  of  piping 
is  provided  to  carry  away  the  condensation,  and  in  some  cases 
also  the  air,  from  the  radiators. 

98.  Single -pipe  System. — The  simplest  form  of  single-pipe 
system  is  that  shown  in  Fig.  59.     The  nearly  horizontal  pipes 
leaving  the  boiler  are  called  the  steam  mains.     The  vertical 
pipes  extending  to  the  upper  floors  are  called  risers.     Steam  is 
generated  in  the  boiler  and  flows  through  the  mains  and  risers 
into  the  radiators,  forcing  the  air  out  ahead  of  it  through  some 
kind  of  an  air  valve  on  the  end  of  the  radiator  opposite  the  sup- 
ply connection.     In  the  system  shown  in  Fig.  59  the  condensation 
formed  in  the  radiators  drains  down  the  risers  into  the  mains  and 
back  to  the  boiler.     The  direction  of  the  flow  of  the  condensation 
is  thus  opposite  to  the  direction  of  the  steam  flow.     In  the  risers 
this  is  not  objectionable  if  the  system  is  small.     In  the  mains, 
however,  the  water  and  steam  flowing  in  opposite  directions  are 
very  liable  to  interfere  with  each  other,  unless  the  mains  are  of 
such  a  diameter  that  the  steam  will  travel  at  a  very  low  velocity. 
If  the  pipes  are  small  so  that  such  interference  takes  place  the 

8  113 


114 


HEATING  AND  VENTILATION 


water  is  picked  up  by  the  steam  and  driven  to  the  end  of 
the  main  with  a  characteristic  loud  cracking  noise  known  as 
"  water-hammer." 

A  better  design  of  a  single-pipe  system  is  shown  in  Fig.  60. 
The  main  pitches  away  from  the  boiler  and  the  condensation 


FIG.  59. — Single-pipe  system — mains  pitching  toward  boiler. 

entering  the  main  from  the  risers  flows  along  with  the  steam. 
The  main  circles  the  basement  and  a  drip  connection  carries  the 
condensation  from  the  end  of  it  to  the  boiler,  entering  below  the 
water  line.  This  is  the  most  common  form  of  single-pipe  system. 
Another  form  of  single-pipe  system,  is  the  single-pipe  relief 


P 


FIG.  60. — Single-pipe  system — mains  pitching  away  from  boiler. 

system  shown  in  Fig.  61.  The  connections  to  the  risers  are 
taken  from  the  bottom  of  the  main  and  a  drip  connection 
is  taken  from  the  foot  of  each  riser  to  a  "wet"  return  main, 
so  called  because  it  is  below  the  water  line  of  the  boiler.  The 
advantage  of  this  method  is  that  no  condensation  from  the  radia- 


STEAM  HEATING  SYSTEMS 


115 


tors  is  carried  by  the  main.  It  also  has  the  advantage  of  allow- 
ing the  main  to  be  placed  close  to  the  basement  ceiling,  which  is 
desirable  if  the  basement  is  used  for  any  purpose  for  which  full 
head  room  is  desired.  This  system  is  sometimes  referred  to  as 
a  two-pipe  system  because  of  its  return  main.  It  will  be  noted, 
however,  that  there  is  only  one  connection  to  each  radiator, 
as  in  the  other  single-pipe  systems. 

The  single-pipe  system  is  simple  in  design  and  can  be  installed 
at  a  low  cost.  It  is  especially  suitable  for  residences  and  small 
buildings  where  a  low-priced  system  is  desired.  In  large  build- 
ings, however,  a  single-pipe  system  is  less  desirable,  on  account  of 
the  large  quantities  of  water  which  must  be  carried  in  the  steam 


a 


o 


a 


.  FIG.  61. — Single-pipe  relief  system. 

mains  and  risers.  Another  objection  is  the  trouble  which  is 
sometimes  experienced  due  to  the  radiators  not  draining  properly. 
If  the  inlet  valve  is  not  closed  tightly  when  the  radiator  is  shut 
off,  or  if  the  valve  leaks,  some  steam  will  continue  to  flow-  into 
the  radiator  and  because  of  the  small  area  of  the  opening  it  is 
impossible  for  the  condensation  to  drain  out  against  the  inflowing 
steam.  As  a  result  the  radiator  becomes  partly  filled  with  water 
and  when  the  valve  is  again  opened  an  annoying  cracking  and 
pounding  takes  place  as  the  water  pours  out  against  the  inrushing 
steam. 

99.  Two-pipe  Systems. — Fig.  62  shows  a  typical  two-pipe 
dry  return  system.  As  the  term  indicates,  the  return  mains 
are  above  the  water  line  of  the  boiler  and  are  filled  with  steam. 
The  supply  mains  and  risers  are  installed  and  connections  taken 
from  them  to  each  radiator  in  much  the  same  manner  as  in  the 
single-pipe  system.  A  " return"  connection  is  made  from  each 


116 


HEATING  AND  VENTILATION 


radiator  to  the  return  main,  through  which  the  condensation 
from  the  radiator  flows.  As  the  steam  has  a  free  passage  through 
the  radiator  from  the  supply  main  to  the  return  main,  it  is  evident 
that  the  latter  will  be  filled  with  steam  at  a  pressure  approaching 
that  in  the  supply  mains,  a  slight  pressure  drop  taking  place 


FIG.  62. — Two-pipe  dry  return  system. 

through  the  radiator  and  its  connections.  The  end  of  each 
supply  main  is  dripped  into  the  return  main  through  a  4  or  5-foot 
water  seal  as  at  b,  b,  which  serves  to  prevent  the  full  steam  pres- 
sure from  entering  the  return  main.  One  of  the  chief  faults  of 
the  two-pipe,  dry  return  system  is  the  tendency  for  the  steam 
to  enter  the  radiator  through  the  return  connection,  especially  if 


FIG.  63. — Wet  return  system. 

the  return  valve  is  opened  first  when  turning  on  the  radiator,  and 
thus  trap  air  in  the  center  of  the  radiator. 

In  the  "wet  return"  system  this  trouble  is  eliminated.  The 
return  main  is  below  the  water  line  of  the  boiler  and  separate 
connections  are  made  to  it  from  each  radiator  and  from  the  low 
points^in  the  supply  mains.  A  wet  return  system  is  shown  in 
Fig.  63. 


STEAM  HEATING  SYSTEMS 


117 


It  is  evident  that  no  steam  can  enter  the  radiator  through  the 
return  connection,  as  the  lower  end  of  each  connection  is  sealed 
with  water.  The  water  level  in  the  return  pipes  is  sometimes  con- 
siderably higher  than  that  in  the  boiler,  as  will  be  evident  upon 
consideration  of  Fig.  63.  If  the  pressure  on  the  surface  of  the 
water  in  the  boiler  is  the  same  as  that  on  the  surface  of  the  water 
in  the  return  lines,  then  the  water  levels  will  be  the  same.  But 
if  a  pressure  of  2  pounds,  for  example,  exists  in  the  boiler  and 
there  is  a  drop  due  to  friction,  of  J^  pound  along  the  main,  then 
the  water  at  (6)  will  rise  'to  a  height  sufficient  to  balance  the  drop 
between  the  boiler  and  the  point  (b).  It  is  necessary,  therefore, 
to  use  pipes  sufficiently  large  so  that  the  pressure  drop  will  not 
be  excessive;  and  furthermore,  no  radiators  should  be  located 


P 

IS 

R 

Q 

1 

fl 

(Z 

~3 

1 

g 

FIG.  64. — Overhead  distribution — single-pipe  system. 

less  than  2  feet  above  the  water  line  of  the  boiler.  The  wet 
return  system  will  usually  operate  with  less  noise  than  a  dry 
return  system  as  the  condensation  does  not  flow  in  horizontal 
pipes  containing  steam.  A  disadvantage  of  two-pipe  systems  is 
the  cost  of  a  double  set  of  radiator  valves,  and  the  nuisance  of 
having  to  operate  both  valves.  Sometimes  a  check  valve  is  used 
instead  of  a  shutoff  valve  on  the  return  end  of  the  radiator,  but 
this  arrangement  is  liable  to  give  more  or  less  annoyance 
from  noise. 

100.  Overhead  System. — In  buildings  over  three  or  four 
stories  high  the  overhead  system  illustrated  in  Fig.  64  is  nearly 
always  used.  The  main  circles  the  attic  and  risers  extend  down 
from  it  to  the  basement,  supplying  the  radiators  on  the  succes- 


118 


HEATING  AND  VENTILATION 


n 


sive  floors.  The  steam  is  carried  to  the  attic  main  by  a  main 
riser  from  which  no  radiators  are  supplied.  The  chief  advantage 
of  the  overhead  system  of  distribution  lies  in  the  fact  that  the 
steam  and  condensation  in  the  risers  are  both  moving  downward. 
Smaller  risers  can  therefore  be  used  without  causing  noise  or 
interfering  with  the  circulation  of  the  system.  The  fact  that 
the  large  piping  is  in  the  attic  rather  than  the  basement  is  also 
an  advantage  when  the  matter  of  head  room  and  appearance  in 
the  basement  is  a  consideration. 

The  overhead  method  of  distribution  may  be  applied  to  either 
the  single-pipe  or  two-pipe  system.  In  the  latter  case,  the  return 
risers  and  the  return  main  are  arranged  in  the  same  manner  as 
in  the  ordinary  upfeed  system. 

101.  Air -line  Systems. — In  the  systems  previously  described, 
the  air  is  discharged  from  the  radiators  through  some  kind  of  an 
air  valve  to  the  atmosphere.  In  order  to  force  the  air  out  of  the 
radiators  the  steam  must  be  at  some  pressure  above  atmosphere, 

and  the  temperature  of  the 
Air  vaive  water  in  the  boiler  must 
be  higher  than  212°.  Con- 
sequently, when  the  fire 
dies  down  or  is  banked  at 
night,  no  steam  is  deliv- 
ered to  the  radiators. 
Furthermore,  when  pres- 
sures only  slightly  above 
atmosphere  exist  in  the 
boiler,  the  radiators  near 
the  boiler  are  wholly  or 
partially  filled  with  steam  while  those  farthest  from  the  boiler 
may  be  cold,  resulting  in  an  uneven  heating  of  the  building. 
Another  objection  to  the  ordinary  means  of  air  removal  is  the 
disagreeable  odor  of  the  air  discharged  and  the  noise  and  fre- 
quent leakage  of  steam  and  water  which  are  characteristic  of 
most  ordinary  air  valves. 

To  overcome  these  objections  a  system  of  air  lines  is  sometimes 
provided  to  convey  the  air  from  all  of  the  radiators  to  a  pump  or 
ejector  located  in  the  basement.  In  place  of  an  ordinary  air 
valve,  an  " air-line  valve"  is  used,  having  a  pipe  connection  on 
the  discharge  side  as  shown  in  Fig.  65  and  designed  to  allow 
iar  to  pass  through  it  but  to  close  against  steam.  By  the  suc- 


Air  Lii 

FIG.  65. — Radiator  in  air  line  system. 


STEAM  HEATING  SYSTEMS 


119 


tion  of  the  pump  or  ejector  a  partial  vacuum  is  maintained  in 
the  air-line  system  and  as  the  steam  output  of  the  boiler  falls 
off  the  vacuum  extends  into  the  radiators,  piping,  and  boiler. 
The  boiling  temperature  is  consequently  reduced  to  the  tempera- 
ture corresponding  to  the  existing  pressure  and  the  boiler  con- 
tinues to  generate  steam  for  a  considerable  time  after  the  fire 
is  banked.  The  circulation  of  the  entire  system  is  also  improved 
and  a  more  even  heating  is  secured.  In  some  cases  no  attempt 
is  made  to  maintain  a  vacuum  on  the  air  lines  and  they  are  open 
to  the  atmosphere,  serving  only  to  eliminate  the  ordinary  air- 
valve  troubles. 

102.  Vapor  Systems. — A  form  of  two-pipe  system  having 
many  desirable  features  is  the  vapor  system,  which  with  slight 
modifications  is  also  variously  termed  "vacuo-vapor, "  "  atmos- 
pheric/' etc.  These  names  are  derived  from  the  fact  that  such 
systems  are  intended  to  operate  on  pressures  but  little  above, 
and  in  some  cases  below  atmosphere.  The  essential  features 
of  vapor  systems  are: 

I.  The  use  of  radiators  of  the  hot-water  type  with  supply  valve 
at  the  top  and  with  return  con- 
nection which  carries  off  both  the 

air  and  condensation. 

II.  The  use  of  a  graduated  supply 
valve  by  means  of  which  the  amount 
of  steam  admitted  to  the  radiator 
can  be  controlled. 

III.  Absence  of  steam  in  the  return 
lines,  which  are  either  open  to  the 
atmosphere    or   under   a   pressure 
less  than  atmosphere. 

The  arrangement  of  a  radiator 
in  a  vapor  system  is  shown  in 
Fig.  66.  By  means  of  a  gradu- 
ated supply  valve  the  steam  supply 
can  be  controlled  so  that  only  the 
amount  required  to  heat  the  room  is  admitted  to  the  radiator. 
The  steam  flows  into  the  successive  sections  of  the  radiator  at 
the  top  and  fills  them  through  part  or  all  of  their  length,  depend- 
ing upon  the  degree  of  valve  opening,  in  the  manner  shown  in 
Fig.  66.  The  surface  of  the  part  of  the  radiator  which  is  filled 
with  steam  is  at  nearly  the  steam  temperature.  The  remainder 


FIG.  66. — Radiator  in  a  vapor 
system. 


120 


HEATING  AND  VENTILATION 


of  the  surface  is  warmed  by  the  condensation  which  trickles  down 
the  inside  surfaces,  the  temperature  decreasing  toward  the  bot- 
tom. The  temperature  of  the  discharged  condensation  is  thus 
materially  lowered  and  in  cases  where  the  condensation  is  not 
returned  to  the  boilers  this  is  an  advantage  from  an  economic 
standpoint. 


FIG.  68. 


FIG.  69. 
Various  forms  of  thermostatic  traps. 

An  important  characteristic  of  vapor  systems  is  that  there  is 
normally  no  steam  in  the  return  lines.  They  carry  both  the 
air  and  condensation  from  the  radiators  and  are  often 
open  to  the  atmosphere.  The  steam  is  prevented  from  flow- 


STEAM  HEATING  SYSTEMS  121 

ing  into  the  return  line  from  the  radiators  by  either  of  two 
means : 

(a)  By  some  device  such  as  a  trap  or  an  orifice  installed  on 
the  return  end  of  the  radiator. 

(6)  By  limiting  the  maximum  area  of  opening  of  the  inlet 
valve  so  that  at  no  time  will  more  steam  be  supplied  to  the 
radiator  than  can  be  condensed  in  it. 

103.  Radiator  Traps. — In  most  vapor  systems  some  kind  of 
a  trap  is  used.     The  most  common  is  the  thermostatic  trap 
which  is  so  constructed  as  to  allow  the  comparatively  cool  air 
and  condensation  to  pass  but  to  close  when  the  steam  at  higher 
temperatures  reaches  it.     Several  forms  of  thermostatic  traps 
are  illustrated  in  Figs.  67,  68  and  69.     All  consist  fundamentally 
of  a  thin-walled  metal  chamber  A  (Fig.  69)  containing  a  volatile 
liquid,  such  as  alcohol,  which  vaporizes  when  heated  and  forms 
sufficient  pressure  inside  the  chamber,  at  a  temperature  of  about 
210°,  to  expand  it  and  bring  the  valve  B  against  the  seat  C.     In 
operation  the  trap  remains  Open  while  air  and  condensation 
pass  though  it  but  when  steam  reaches  it  and  heats  the  thermo- 
static element  it  closes,  and  remains  closed  until  the  condensation 
accumulating  in  it  cools  a  few  degrees,  causing  it  to  open  again 
and  discharge  the  condensation. 

Another  type  of  radiator  trap  is  the  float  trap  in  which  the 
opening  and  closing  of  the  valve  is  dependent  entirely  upon  the 
flow  of  condensation  into  the  trap.  The  chief  objection  to 
float  traps  is  that  they  are  sometimes  noisy  in  operation  and 
are  then  a  source  of  annoyance  to 
the  occupants  of  the  room.  Also, 
there  is  a  tendency  for  some  leak- 
age of  steam  through  the  trap  to 

,     ,          ,  Water 

take  place. 

104.  Retarders.  — While      the 

thermostatic    and    float   traps  are 

designed  to  close  positively  against  FIG.  70.— Retarder. 

the  steam,  another  type  of  return 

fitting   is   used    which    only   restricts   its   passage,    allowing   a 

small  amount  to  pass  into  the  return  line  when  the  radiator  is 

filled  with  steam.     This  is  not  objectionable  as  the  leakage  is 

usually  so  slight  that  it  is  condensed  in  the  return  lines.     Re- 

tarders  are  usually  in  the  form  of  an  orifice  as  in  Fig.  70.     These 

fittings  have  the  advantages  of  being  of  low  cost,  of  simple 


122  HEATING  AND  VENTILATION 

construction,  and  of  requiring  no  adjustment.  For  systems  of 
moderate  size  they  are  quite  satisfactory.  If,  however,  the 
pressure  regulation  is  such  that  a  pressure  of  over  a  few  ounces 
may  exist  in  the  system  there  is  a  possibility  of  an  excessive 
amount  of  steam  leaking  into  the  return  lines,  which  is  very 
undesirable.  Such  fittings  are  often  used  in  connection  with 
a  supply  valve  having  a  restricted  opening  such  as  those  used  in 
the  atmospheric  system  described  in  the  next  paragraph. 

105.  Atmospheric  Systems. — The  primary  function  of  the 
return  fittings  previously  described  is  to  prevent  or  restrict  the 
leakage  of  steam  into  the  return  line.  In  the  so-called  atmos- 
pheric system  this  is  accomplished  in  another  way — by  restrict- 
ing the  supply  so  that  there  will  be  no  uncondensed  steam  to 
overflow  into  the  return  line.  In  such  systems  no  special 
return  fitting  is  provided  and  the  return  line  is  connected  direct 
to  the  radiator.  The  maximum  area  of  opening  of  the  supply 
valve  when  in  its  wide  open  position  is  restricted  by  means  of 
an  orifice  disc,  for  example,  so  that  with  an  assumed  pressure  in 
the  supply  pipe — usually  about  5  ounces — only  the  amount  of 
steam  which  the  radiator  will  condense  can  enter  it.  It  is  evident 
that  the  amount  of  steam  which  will  pass  through  the  maximum 
opening  of  the  supply  valve  will  vary  with  the  pressure  in  the 
supply  pipe.  Therefore  any  pressure  less  than  that  for  which 
the  system  is  designed  will  not  cause  sufficient  steam  to  enter 
the  radiator  in  the  coldest  weather.  Any  considerable  increase 
in  pressure  above  this  amount  will  force  more  steam  through  the 
valve  than  the  radiator  will  condense  and  the  excess  will  enter 

the  return  piping.  If  the  system 
has  been  carefully  designed,  so  that 
at  any  one  time  nearly  the  same 
pressure  exists  at  the  supply  con- 
nections of  all  the  radiators,  and 
if  the  pressure  is  closely  regulated 
at  the  boiler,  the  atmospheric 

scheme  is  1uite  successful  in  sys- 
terns  of  moderate  size. 
When  the  water  of  condensation  is  not  returned  to  the  boiler, 
as  often  happens  when  steam  is  obtained  from  a  central  heating 
plant,  it  is  always  desirable  to  utilize  the  sensible  heat  in  the 
condensation.  Atmospheric  systems  accomplish  this  very  effec- 
tively, the  heat  being  removed  as  the  condensation  flows  down 


STEAM  HEATING  SYSTEMS 


123 


the  walls  of  a  partly  filled  radiator  and  through  the  uncovered 
return  piping.  In  systems  where  the  steam  supply  is  restricted 
at  the  inlet  valves  the  radiators  are  sometimes  given  from  10 
to  20  per  cent,  more  surface  than  is  required,  so  that  at  no  time 
will  they  be  entirely  filled  and  the  lower  portions  are  always 
available  for  removing 
the  sensible  heat  of  the 
condensation. 

106.  Supply  Valves. 
The  supply  valves 
of  vapor  systems  are 
of  two  classes — those 
which  limit  and  those 
which  do  not  limit  the 
amount  of  steam  which 
can  enter  the  radiator 
when  the  valve  is  in 
the  wide  open  position. 
In  Fig.  71  is  shown  a 
valve  of  the  second  type.  The  full  opening  can  be  obtained  by 
a  half  turn  of  the  lever  handle  and  the  degree  of  opening  is  always 
readily  discernible.  The  valve  can  be  partly  opened  according 
to  the  amount  of  heat  required.  Fig.  72  shows  one  form  of  valve 
whose  maximum  opening  may  be  restricted  according  to  the 


FIG.  72. — Supply  valve — maximum  opening 
restricted. 


FIG.  73. — Vapor  system. 

size  of  the  radiator  on  which  it  is  to  be  used.  The  maximum 
movement  of  the  handle  is  fixed  by  the  stop  (d)  which  is  adjusted 
when  the  system  is  first  put  into  service. 

107.  General  Arrangement  of  Vapor  Systems. — The  arrange- 
ment of  the  supply  and  return  piping  of  a  vapor  system  is  shown 


124  HEATING  AND  VENTILATION 

in  Fig.  73.  The  air  is  forced  out  of  the  radiators  by  the  entering 
steam  and  passes  through  the  return  piping  to  the  air  vent 
located  near  the  boiler.  The  supply  main  pitches  away  from 
the  boiler  and  is  dripped  at  the  end  by  means  of  a  trap  similar 
to  those  used  on  the  radiators  or  by  a  seal. 

108.  Removal  of  Air  from  Return  Piping. — Many  different 
luethods  are  employed  for  venting  the  air  from  the  return  piping. 
The  simplest  arrangement  is  to  leave  the  return  line  open  at  all 
times  to  the  atmosphere ;  but  to  provide  against  leakage  of  steam 
in  case  of  the  failure  of  a  radiator  trap  to  close,  a  special  vent 
valve  is  often  provided  which  is  normally  open  and  closes  only 
when  steam  reaches  it.     These  vent  valves  are  quite  similar  in 
principle  to   the   ordinary  thermostatic  radiator   trap.     Float 
valves,  or  combination  float  and  thermostatic  valves,  are  fre- 
quently used,  their  function  being  to  close  when  water  reaches 
them  and  thus  to  guard  against  leakage  in  case  of  the  accidental 
flooding  of  the  return  piping. 

Some  vent  valves  include  also  a  check-valve  arrangement 
which  allows  air  to  escape  from  the  system  but  prevents  it  from 
reentering.  The  air  is  driven  out  of  the  system  when  the  radia- 
tors and  piping  fill  with  steam;  and  as  the  steam  output  of  the 
boiler  decreases,  the  pressure  falls  below  atmosphere  and 
the  boiler  continues  to  generate  steam  after  the  temperature  of 
the  water  in  it  has  dropped  below  212°,  as  is  the  case  in  a 
vacuum  system. 

109.  Advantages  of  Vapor  Systems. — It  is  apparent  that  for 
many  classes  of  buildings  vapor  systems  have  some  advantages 
over  the  other  systems  of  heating,  which  may  be  summarized 
as  follows : 

1.  Control  of  the  Heat  Supply. — This  is  accomplished  by  the 
manipulation  of  the  supply  valves  and  is  therefore  dependent 
for  its  effectiveness  upon  the  attention  of  the  occupants  of  the 
room.     The  improved  design  of  inlet  valve  and  its  accessible 
location  at  the  top  of  the  radiator  render  it  convenient  to  operate, 
although  in  many  classes  of  buildings  the  occupants  are  not 
inclined  to  make  use  of  this  means  of  heat  control. 

2.  Circulation    on    Very   Low    Pressures. — This    is    of    some 
advantage  from  the  standpoint  of  economy,  but  is  shared  by  the 
various  kinds  of  vacuum  systems. 

3.  Noiseless  Operation. — As  the  steam  and  water  flow  in  sepa- 
rate systems  of  piping  there  is  no  opportunity  for  water-hammer. 


STEAM  HEATING  SYSTEMS 


125 


4.  Discharge   of  Air   into    the   Basement   Instead   of  into  the 
Rooms. — This  eliminates  the  noise,  smell,  and  drip  which  accom- 
pany the  action  of  the  ordinary  air  valve. 

5.  Economy  of  Operation. — The  opportunity  afforded  for  accu- 
rate temperature  regulation  coupled  with  the  possibility  of  circu- 
lation on  very  low  pressures  are  productive  of  some  economy. 
The  measure  of  saving  obtained,  however,  is  rather  uncertain. 

The  disadvantages  of  vapor  systems  are  the  cost  of  the  special 
fittings  and  appliances  and  the  maintenance  of  the  radiator  traps. 

110.  Vacuum  Return  Line  Systems. — In  a  "  vacuum  return 
line"  system  radiators  of  the  hot  water  type  may  be  used,  the 


FIG.  74. — Steam-driven  vacuum  pump. 

arrangement  being  similar  to  that  of  a  vapor  system,  or  steam 
radiation  can  be  used  with  the  inlet  valve  at  the  bottom.  In 
either  case  some  form  of  trap  is  provided  on  the  radiators  and  a 
vacuum  pump  is  connected  to  the  return  main. 

If  a  high-pressure  steam  supply  is  available,  a  steam-driven 
purnp  exhausting  into  the  heating  system  is  the  most  economical 
as  regards  the  energy  consumed,  but  motor-driven  pumps  have 
the  advantage  of  requiring  much  less  attention  and  maintenance. 
A  simple  plunger  pump  is  shown  in  Fig.  74.  Pumps  of  this  type 
can  be  built  to  operate  on  steam  pressures  as  low  as  10  pounds 
but  this  necessitates  a  very  large  steam  cylinder.  In  general, 
unless  steam  of  at  least  25  pounds  pressure  is  available,  it  is 
better  to  use  a  motor-driven  pump. 

For  the  proper  operation  of  a  vacuum  system  it  is  essential 
that  the  traps  on  the  radiators  be  in  good  condition  and  close 


i'y    /< 


126  HEATING  AND  VENTILATION 

tightly.  If  they  do  not  close  tightly  a  leakage  of  steam  into  the 
return  pipes  will  occur  which  will  make  it  very  difficult  to  main- 
tain the  vacuum.  A  water  spray  at  the  vacuum  pump  suction 
is  often  used  to  condense  any  steam  which  may  be  present,  but 
the  use  of  an  excessive  amount  of  spray  water  is  a  source  of 
considerable  loss,  as  the  spray  water  must  necessarily  be  wasted, 
carrying  with  it  the  latent  heat  of  the  steam  which  it  has 
condensed. 

One  of  the  advantages  of  vacuum  systems — the  continued 
generation  of  steam  at  temperatures  below  212° — has  already 
been  brought  out  (Par.  101).  Another  important  advantage  is 
the  better  circulation  in  both  supply  and  return  pipes  produced 
by  the  greater  pressure  differential.  If,  for  example,  a  vacuum 
system  is  operated  with  a  steam  pressure  of  2  pounds  and  a 
vacuum  of  10  inches  of  mercury,  the  total  differential  is  about 
7  pounds.  A  more  rapid  warming  up  of  the  system,  better 
removal  of  air  from  the  radiators,  and  better  circulation  in  return 
lines  having  air  or  water  pockets  are  other  advantages  which 
might  be  mentioned.  In  case  some  radiators  are  located,  per- 
force, below  the  water  line  of  the  boiler  a  vacuum  pump  must 
be  used  to  drain  them  properly.  From  the  standpoint  of  economy 
vacuum  systems  are  of  some  advantage  because  of  the  lower 
radiator  temperatures  which  exist  if  a  vacuum  is  carried  on  the 
entire  system  at  times  when  less  heat  is  needed.  When  exhaust 
steam  is  used  for  heating  a  vacuum  system  permits  of  a  lower 
back  pressure  on  the  engines  and  turbines  and  therefore  im- 
proves the  economy  of  the  plant.  Vacuum  systems  are  best 
suited  to  large  buildings  where  the  advantages  to  be  gained 
will  justify  their  initial  cost  and  operating  cost. 


CHAPTER  IX 
PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES 

111.  Pipe. — The  pipe  used  for  the  conveying  of  steam  and 
water  is  made  of  either  cast  iron,  wrought  iron,  or  steel.  Because 
of  the  low  tensile  strength  of  cast  iron,  pipe  made  of  this  material 
is  suitable  only  for  low  pressures,  and  must  have  a  relatively 
thick  wall.  Owing  to  its  ability  to  withstand  corrosion  it  is 
especially  adaptable  for  use  where  it  must  be  buried  in  soil. 
Cast-iron  pipe  is  seldom  used  in  heating  work. 

The  pipe  ordinarily  used  in  heating  and  power  plants  is  made 
from  wrought  iron  or  mild  steel.  Steel  pipe  is  much  more  widely 
used  than  wrought-iron  pipe  at  the  present  time,  being  con- 
siderably lower  in  price  and  for  many  purposes  equally  as  desir- 
able as  wrought-iron  pipe.  The  pipe  commonly  furnished  to  the 
purchaser  under  the  name  of  wrought-iron  pipe  is  likely  to  be  steel 
pipe,  so  that  if  wrought-iron  pipe  is  desired  it  must  be  clearly 
specified.  It  is  rather  difficult  to  distinguish  between  the  two 
materials  except  by  a  chemical  test.  The  threads  cut  upon  steel 
pipe  with  an  ordinary  threading  die  are  usually  somewhat  the 
more  ragged,  however,  and  this  affords  a  rough  means  of  identi- 
fication. Wrought-iron  pipe  is  believed  by  many  to  be  more 
resistant  to  corrosion  than  steel  pipe,  but  the  degree  of  superiority 
in  this  respect,  if  both  kinds  are  well  made,  is  often  questioned. 

In  the  manufacture  of  wrought  pipe  the  strips  of  metal,  cut  to 
the  proper  width,  are  drawn  through  a  bell  to  the  cylindrical  form 
and  the  edges  welded  together.  In  pipe  of  the  smaller  diameters 
a  "butt"  weld  is  used  and  in  the  larger  sizes  a  "lap"  weld. 

Wrought-iron  and  steel  pipe  are  furnished  in  sizes  ranging  from 
%  inch  to  30  inches  nominal  diameter.  In  the  sizes  up  to  14 
inches  the  nominal  diameters  correspond  approximately  with 
the  inside  diameter  of  the  pipe,  while  in  the  larger  sizes  the  pipe 
is  designated  by  its  outside  diameter.  The  nominal  and  actual 
dimensions  of  wrought-iron  and  steel  pipe  are  given  in  Table 
XXVII.  Ordinarily  it  is  not  desirable  to  use  the  3^,  4J^,  7, 
9,  and  11-inch  sizes  unless  necessary,  as  these  are  regarded  as 
odd  sizes  and  their  use  is  being  gradually  discontinued.  For 

127 


128 


HEATING  AND  VENTILATION 


working  pressures  of  over  150  pounds  "  full-weight "  pipe  should 
be  specified.  Such  pipe  is  selected  as  being  of  full  card  weight 
per  running  foot,  while  ordinary  pipe  varies  somewhat  from  the 


TABLE  XXVII. — STANDARD   WROUGHT   STEAM,    GAS   AND   WATER   PIPE 
Table  of  Standard  Dimensions 


. 

Circum- 

Transverse 

Diameter 

ference 

areas 

Length 

j 

of  pipe 
per 

Length 
of  pipe 

Nomi- 
nal 

Number 

Nomi- 
nal 
inter- 

Exter- 
nal, 

Ap- 
proxi- 
mate 

Exter- 
nal, 

Inter- 
nal, 

Exter- 
nal, 

Inter- 
nal, 

square 
foot  of 
exter- 

contain- 
ing 1 
cubic 

weight 
per 
foot, 

of 
threads 

nal, 
inches 

inches 

inter- 
nal 

inches 

inches 

square 
inches 

square 
inches 

nal 
surface 

foot, 
feet 

plain 
ends 

inch  of 
screw 

diam., 

feet 

inches 

I 

H 

0.405 

0.269 

1.272 

0.845 

0.129 

0.057 

9.431 

2,533.775 

0.244 

27 

\i 

0.540 

0.364 

1.696 

1.144 

0.229 

0.104 

7.073 

1,383.789 

0.424 

18 

% 

0.675 

0.493 

2.121 

1.549 

0.358 

0.191 

5.658 

754  .  360 

0.567 

18 

K 

0.840 

0.622 

2.639 

1.954 

0.554 

0.304 

4.547 

473  .  906 

0.850 

14 

H 

1.050 

0.824 

3.299 

2.589 

0.866 

0.533 

3.637 

270.034 

1.130      14 

l 

1.315 

1.049 

4.131 

3.296 

1.358 

0.864 

2.904 

166.618 

1.678      11H 

IK 

1.660 

1.380 

5.215 

4.335 

2.164 

1.495 

2.301 

96.275 

2.272      11}.$ 

1H 

1.900 

1.610 

5.969 

5.058 

2.835 

2.036 

2.010 

70.733 

2.717 

UH 

2 

2.375 

2.067 

7.461 

6.494 

4.430 

3.355 

1.608 

42.913 

3.652 

11  ^ 

2M 

2.875 

2.469 

9.032 

7.757 

6.492 

4.788 

1.328 

30.077 

5.793 

8 

3 

3.500 

3.068 

10.996 

9.638 

9.621 

7.393 

1.091 

19.479 

7.575 

8 

3H 

4.000 

3.548 

12.566 

11.146 

12.566 

9.886 

0.954 

14.565 

9.109 

8 

4 

4.500 

4.026 

14.137 

12.648 

15.904 

12.730 

0.848 

11.312 

10.790 

8 

4>6 

5.000 

4.506 

15.708 

14.156 

19,635 

15.947 

0.763 

9.030 

12.538 

8 

5 

5.563 

5.047 

17.477 

15.856 

24.306 

20.006 

0.686 

7.198 

14.617 

8 

6 

6.625 

6.065 

20.813 

19.054 

34.472 

28.891 

0.576 

4.984 

18.974 

8 

7 

7.625 

7.023 

23.955 

22  .  063 

45.664 

38  .  738 

0.500 

3.717 

23  .  544 

8 

8 

8.625 

8.071 

27.096 

25  .  356 

58.426 

51.161 

0.442 

2.815 

24  .  696 

8 

8 

8.625 

7.981 

27.096 

25.073 

58  .  426 

50.027 

0.442 

2.878 

28.554 

8 

9 

9.625 

8.941 

30.238 

28.089 

72.760 

62.786 

0.396 

2.294 

33.907 

8 

10 

10.750 

10.192 

33.772 

32.019 

90.763 

81.585 

0.355 

1.765 

31.201 

8 

10 

10.750 

10.136 

33.772 

31.843 

90.763 

80.691 

0.355 

1.785 

34  .  240 

8 

10 

10.750 

10.020 

33  .  772 

31.479 

90  .  763 

78.855 

0.355 

1.826 

40.483 

8 

11 

11.750 

11.000 

36.914 

34  .  558 

108.434 

95.033 

0.325 

1.515 

45.557 

8 

12 

12.750 

12.090 

40.055 

37.982 

127.676 

114.800 

0.299 

1.254 

43.773 

8 

12 

12.750 

12.000 

40.055 

37.699 

127.676 

113.097 

0.299 

1.273 

49.562 

8 

13 

14.000 

13.250 

43.982 

41.626 

153.938 

137.886 

0.272 

1.044 

54.568 

8 

14 

15.000 

14.250 

47.124 

44.768 

176.715 

159.485 

0.254 

0.903 

58  .  573 

8 

15 

16.000 

15.250 

50.265 

47.909201.062 

I 

182.654 

0.238 

0.788 

62.579 

8 

standard  weight  because  of  slight  variations  in  the  thickness  of 
the  sheets  from  which  it  is  made.  For  extremely  high  pressures, 
"extra  strong "  and  "double  extra  strong"  pipe  may  be  obtained. 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  129 


The  extra  thickness  of  the  walls  is  added  on  the  inside  of  the  pipe, 
reducing  the  internal  area  and  not  affecting  the  outside  diameter. 
These  heavier  grades  are  seldom  used  in  heating  work. 

112.  Pipe  Threads. — In  order  that  they  may  be  screwed  to  a 
tight  joint,  pipe  threads  are  made  with  a  taper  of  1  in  32  with  the 
axis  of  the  pipe,  and  the  threads  in  the  fittings  are  tapped  to  the 
same  taper.  Pipe  threads  are  commonly  made  to  conform  to 
the  so-called  Briggs  standard,  illustrated  in  Fig.  75,  which  calls 
for  a  thread  having  a  60-degree  angle,  with  the  top  and  bottom 
slightly  flattened.  The  number  of  threads  per  inch  varies  for  the 
different  sizes  of  pipe. 


8  or  4  Threads, 


Imperfect 
Top  and  Bottom 


2  Threads 


Perfect 

at  Root 

Imperfect 

at  Top 


\^60  -w" 


VVWvWW 


FIG.  75. — Briggs  standard  pipe  thread. 

113.  Screwed  Fittings. — The  common  forms  of  screwed  fittings 
used  in  heating  work  are  shown  in  Fig.  76.     All  except  the 
nipples  and  ordinary  coupling  are  made  of  cast  iron.     In  desig- 
nating reducing  tees  the  size  of  the  openings  opposite  each  other 
is  given  first  and  then  the  size  of  the  branch  opening.     For 
example,  the  reducing  tee  in  Fig.  76  is  a  1J^  by  1  by  J^-inch  tee. 

For  pressures  over  125  pounds,  an  " extra  heavy"  pattern  is 
available  which  is  suitable  for  working  pressures  up  to  250 
pounds.  Extra  heavy  fittings  are  made  with  a  greater  wall  thick- 
ness and  are  of  larger  dimensions  throughout. 

114.  Unions. — Where  screwed  fittings  are  used,  provision  should 
be  made,  at  intervals  in  the  line,  for  disconnecting  the  piping 
for    repairs,    etc.     " Right    and   left"    couplings    or    "unions" 
are  used  for  this  purpose.     The  former,  as  the  name  indicates,  are 
couplings  tapped  at  one  end  with  a  left-hand  thread,  so  that  both 
threads  can  be  screwed  up  simultaneously.     Longitudinal  ridges 
are  cast  on  right  and  left  couplings  so  that  they  can  be  identified 
after  installation. 

For  pipe  sizes  up  to  2  inches,  nut  unions,  consisting  of  two 


130 


HEATING  AND  VENTILATION 


pieces  screwed  to  the  ends  of  the  pipe  and  held  together  by 
means  of  a  threaded  nut  are  used.  Flanged  unions  are  used 
with  larger  sizes  of  pipe.  In  Fig.  77  are  shown  these  various 


90  Elbow- 


Cross 


45  .Elbow 


Reducing 
Elbow 


Reducing 
Tee 


Reducing 
Coupling 


Plug 


Cap 


Bushing 


Coupling 


Close  Nipple  Shoulder  Nipple 

FIG.  76.— Screwed  fittings. 

types  of  pipe  connections.  The  ground-joint  union  is  superior 
to  the  gasket  union  in  that  it  can  be  disconnected  repeatedly 
without  trouble,  whereas  the  gasket  in  the  latter  type  must  be 
frequently  replaced. 


Brass 


Lap  Union 


Iron 

Iron,  and  Brass  Iron  Union  with 

Union  Brass  Seat  Ring 

FIG.  77. — Pipe  unions. 


115.  Flanged  Fittings. — In  heating  work,  piping  of  the  larger 
sizes  (over  3  or  4  inch)  is  usually  designed  with  flanged  connec- 
tions, in  order  that  any  section  of  pipe  or  any  fitting  can  be 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  131 


readily  removed.  With  screwed  fittings  it  is  necessary,  in  order 
to  remove  any  member,  to  take  down  all  of  the  line  from  the 
nearest  union  or  flanged  connection.  Flanges  are  commonly 
screwed  to  the  pipe,  especially  for  low-pressure  work.  For  high- 
pressure  work  they  may  be  welded  to  the  pipe  or  attached  by  the 


.Screwed  Flange  Welded  Flange 

FIG.  78. — Various  forms  of  flanges. 


Improved  Van  Stone 
Flange 


"Van  Stone"  method  in  which  the  pipe  extends  through  the 
flange  and  is  formed  to  a  flat  face  as  shown  in  Fig.  78. 

Some  forms  of  standard  weight  flanged  fittings  are  shown  in 
Fig.  79.  These  fittings  are  suitable  for  pressures  up  to  125 
pounds.  There  is  an  extra  heavy  pattern  of  flanges  and  flanged 


90  Elbow 


45  Elbow 


Reducer 


Reducing  Tee 


Tee 

FIG.  79. — Flanged  fittings. 


Cross 


fittings  which  differ  both  in  general  dimensions  and  in  the  number 
and  spacing  of  the  bolts. 

116.  Gaskets. — In  bolting  together  flanged  fittings  it  is  neces- 
sary to  insert  a  gasket  between  the  faces  in  order  to  insure  a 
tight  joint.  Gaskets  are  made  of  sheet  rubber  for  water  and 
low-pressure  steam  lines;  for  high-pressure  lines  gaskets  of 


132 


HEATING  AND  VENTILATION 


corrugated  copper  or  of  various  compositions  containing  asbestos 
are  used.  Gaskets  are  preferably  cut  in  a  plain  ring  to  fit  inside 
of  the  flange  bolts. 

117.  Valves. — In  Fig.  80  are  shown  the  various  types  of  valves. 
The  gate  valve  is  the  form  ordinarily  used  in  steam  piping. 


Iron  body  gate 
valve  non-ris- 
ing stem. 


Iron  body  globe  valve 
rising  stem. 


Angle  valve. 


All  bra^s  gate  valve. 


All  brass  globe  valve. 
FIG.  80. 


Swing  check  valve. 


Globe  valves  are  not  permissible  in  horizontal  steam  lines  as  they 
are  so  constructed  as  to  dam  up  the  water  and  cause  it  to  accumu- 
late in  the  bottom  of  the  pipe,  but  on  vertical  steam  pipes  and  on 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  133 


water  pipes  they  are  permissible  and  are  especially  desirable 
when  the  flow  of  steam  or  water  is  to  be  throttled.  The  angle 
valve  is  a  very  good  type  of  valve  for  locations  where  it  can  be 
used. 

Valves  in  sizes  up  to  3  inches  are  made  entirely  of  brass  and 
the  larger  sizes  are  usually  made  of  cast  iron,  with  the  gates  and 
seats  faced  with  bronze  to  give  a  non-corroding  surface.  The 
bronze  mountings  can  be  replaced  when  worn.  The  covei  or 
bonnet  of  these  larger  valves  is  bolted  instead  of  screwed  to 
the  body.  Gate  valves  are  made  either  with  a  rising  or 
non-rising  stem.  With  a  rising  stem  valve  the  amount  to 
which  the  valve  is  open  is  always  apparent,  which  is  often  of 
great  advantage  but  the  space  occupied  by  the  valve  is  somewhat 
greater.  * 

Check  valves  are  frequently  used  in  heating  work.  The  swing 
check  illustrated  in  Fig.  80  is  the  most  satisfactory  form. 

118.  Radiator  Valves. — The  ordinary  radiator  valve  for  steam 
is  of  the  angle  pattern  and  is  provided  with  a  union  for  connecting 
to  the  radiator,  as  shown  in  Fig.  81. 
The  valve  disc  is  made  of  hard  rubber 
and  is  renewable.  These  valves  are 
also  made  in  the  " corner"  pattern. 

The  stem  of  the  ordinary  radiator 
valve  is  packed  to  prevent  leakage 
with  a  soft  stranded  packing.  The 
packing  is  seldom  permanently  tight, 
however,  and  the  resulting  leakage  is 
often  a  source  of  considerable  annoy- 
ance. In  the  more  modern  valves  the 
packing  is  replaced  by  a  grooved  hard- 
rubber  washer  which  is  held  against  a 
seat  by  a  spring.  The  construction 
of  these  so-called  "packless"  valves  is 
shown  in  Fig.  82.  Valves  so  con- 
structed are  much  superior  to  the  ordi- 

nany  type,  as  all  leakage  and  the  necessity  of  renewing  the 
packing  are  eliminated. 

The  ordinary  steam-radiator  valve  may  be  used  in  hot-water 
work.  A  special  hot-water  valve  is  made,  however,  which 
consists  of  a  sleeve  having  an  orifice  equal  to  the  pipe%rea.  By 
a  half  turn  of  the  hand-wheel  the  sleeve  is  turned  so  that  the 


FIG.  81. — Ordinary  radiator 
valve. 


134 


HEATING  AND  VENTILATION 


orifice  is  brought  opposite  the  opening  to  the  radiator.  When 
closed,  the  valve  allows  enough  circulation  through  the  radiator 
to  prevent  freezing.  Fig.  83  shows  a  valve  of  this  type. 


FIG.  82. — Packless  valve. 


FIG.  83. — Hot  water  radiator 
valve. 


119.  Pipe  Covering. — The  piping  of  a  heating  system  which  is 
not  intended  to  serve  as  radiating  surface  is  insulated  with  some 
material  of  low  heat  conductivity.  Most  insulating  materials 
owe  their  useful  property  to  air  enclosed  in  extremely  small 
volumes.  If  the  material  is  to  be  an  efficient  insulator  these  air 
volumes  must  be  so  minute  that  the  circulation  of  the  air  in  them 
is  reduced  to  a  minimum  and  in  addition,  the  material  itself  must 
be  of  low  conductivity.  A  satisfactory  pipe  covering  must  also 
be  able  to  withstand  the  effect  of  high  temperature  and  vibration, 
and  to  retain  its  insulating  qualities  throughout  a  long  period  of 
years.  Pipe  coverings  are  made  of  magnesia,  asbestos,  infusorial 
earth,  hair  felt,  wool  felt,  and  other  materials.  These  substances 
form  the  basic  element  and  are  usually  combined  with  other 
materials  for  mechanical  reasons. 

The  material  which  is  probably  the  most  widely  used  as  an 
insulator  is  magnesium  carbonate.  It  is  in  the  form  of  a  white 
powder,  and  some  fibrous  material  such  as  asbestos  fibers  must 
be  used  with  it  as  a  binder,  the  aggregate  being  molded  into 
blocks  or  into  segments  curved  to  fit  the  various  sizes  of  pipe. 
Infusorial  earth,  which  consists  of  the  siliceous  shells  of  minute 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  135 

organisms,  is  also  combined  with  various  binding  materials  to 
form  a  very  efficient  covering. 

Many  forms  of  pipe  covering  are  made  of  asbestos  in  combina- 
'tion  with  some  cellular  material.  The  compound  is  rolled  into 
sheets  and  the  covering  built  up  in  corrugations  so  as  to  enclose 
air  spaces.  While  not  the  most  efficient  type,  these  coverings 
are  often  the  most  suitable  because  of  their  low  price.  Fig.  84 
shows  a  covering  of  this  type.  Hair  felt,  composed  of  matted 
cattle  hair,  is  very  efficient  but  cannot  be  placed  in  direct 
contact  with  steam  pipes  owing  to  its  tendency  to  char  at  steam 
temperatures. 

In  the  selection  of  a  pipe  covering  the  cost  of  the  pipe  covering 
should  be  balanced  against  the  saving  which  is  effected  by  the 
reduction  of  the  heat  loss  from  the  piping.  Tests  have  recently 
been  made  on  commercial  pipe  coverings  by  L.  B.  McMillan  and 


FIG.  84. — Cellular  pipe  covering. 

the  results  of  his  extensive  investigations  are  shown  by  the  curves 
in  Fig.  85  which  give  the  heat  loss  through  several  commercial 
coverings  of  standard  thickness  for  various  temperature  differ- 
ences between  the  surface  of  the  pipe  and  the  air. 

It  is  nearly  always  desirable  to  provide  insulation  on  the  boiler 
and  on  the  basement  and  attic  mains  in  a  heating  system.  It  is 
usually  desirable  to  cover  also  the  supply  risers,  because  they 
would  otherwise  give  off  heat  continuously  whether  needed  or 
not.  Return  risers  are  seldom  covered  in  a  system  equipped  with 
thermostatic  traps. 

It  is  seldom  proper,  in  heating  work,  to  install  the  most  effi- 
cient covering,  as  the  cost  of  such  a  covering  may  easily  offset 
the  decrease  in  heat  loss  obtained.  In  fact,  the  heat  radiated 
from  the  covered  mains  and  risers  of  a  heating  system  is  not 
entirely  a  loss  as  it  is  partially  utilized.  In  general,  where  the 


136 


HEATING  AND  VENTILATION 


steam  temperature  is  high,  the  service  continuous,  and  the  coal 
expensive  a  more  efficient  covering  is  called  for  than  in  the  case 
of  low  steam  pressure  and  intermittent  service,  with  a  low-priced 
coal. 


0.95 
0.90 
0.85 


0.70 


No.VII  Sail-Mo  Expanded 
No.VI  J-M  Wool  Felt 
No.IV  J-M  Eureka 
No.X  Carey  Duplex 
No.XIX  Plastic  85%M,agnesi 
No. XII   Sail-Mo  Wool  Felt 


"0         50        100150200        250300        350400        450       500 
Temperature  Difference,  Degrees  Fahrenheit 
(Pipe  Temp  .-Boom  Temp.) 

FIG.  85. — Results  of  tests  by  L.  B.  McMillan  on  single  thickness  pipe  coverings. 


120.  Covering  for  Boilers  and  Fittings. — The  exposed  surfaces 
of  heating  boilers  are  usually  covered  with  an  insulating  cement, 
containing  asbestos  fibers  and  some  sort  of  a  filler.  The  cement 
is  applied  to  the  hot  boiler  with  the  hand  to  a  depth  of  from  1  to 
2  inches  and  bound  with  wire,  after  which  a  finishing 'coat  of 
cement  and  a  canvas  jacket  are  applied.  The  pipe  fittings  are 
also  covered  with  cement  to  the  same  thickness  as  that  of  the 
pipe  covering.  For  large  flanges  and  fittings  removable  cover- 
ings can  be  obtained  which  allow  repeated  access  to  the 'joints 
without  damage  to  the  covering. 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  137 


121.  Air  Valves. — In  the  ordinary  steam  heating  system  the 
air  which  fills  the  radiators  when  they  are  cold  is  forced  out  by 
the  entering  steam  through  some  form  of  air  valve  installed  on 
the  end  of  the  radiator  opposite  the  supply  connection.  These 
air  valves  may  be  simply  hand-operated  cocks,  which  must  be 
opened  whenever  the  radiator  is  turned  on,  but  the  many  forms 
of  air  valves  which  allow  the  air  to  escape  but  close  automatically 
when  steam  reaches  them,  are  greatly  to  be  preferred.  Auto- 
matic air  valves  are  also  designed  to  close  when  flooded  with  water 
as  sometimes  happens  when  a  radiator  does  not  drain  properly 


FIG.  86. 


FIG.  87. 


FIG.  88. — Riser  vent. 


or  becomes  filled  with  water  because  of  a  leaky  inlet  valve. 
The  common  design  is  illustrated  in  Fig.  86.  The  composition 
post  A  expands  when  steam  reaches  it,  causing  the  valve  stem  B 
to  close  against  its  seat.  If  water  reaches  the  valve  the  inverted 
cup  C,  to  which  the  valve  stem  B  is  attached,  is  raised  by  the 
buoyancy  of  the  enclosed  air  and  the  valve  closes.  The  force 
thus  developed  for  closing  the  valve  is  small,  however,  and  these 
valves  cannot  therefore  be  depended  upon  to  prevent  entirely 
the  escape  of  water.  The  valve  shown  in  Fig.  87  operates  on  the 
same  general  principle,  the  expansion  of  a  volatile  fluid  in  the 
cylinder  acting  to  close  the  valve  when  the  steam  reaches  it 
and  the  cylinder  serving  as  a  float  which  closes  the  valve  when 
water  reaches  it.  While  more  expensive,  this  form  of  air  valve 
is  more  reliable  than  the  cheaper  grades.  It  is  always  desirable 


138 


HEATING  AND  VENTILATION 


to  use  air  valves  of  good  quality,  as  the  faulty  operation  of  an 
air  valve  is  a  source  of  extreme  annoyance. 

Where  large  quantities  of  air  are  to  be  handled  as  in  the  case  of 
a  large  riser  or  main,  it  is  better  to  install  a  valve  with  a  larger 
opening  than  that  of  the  ordinary  radiator  air  valve,  so  that  the 
air  can  be  discharged  in  a  short  time.  Such  air  valves  are  com- 
monly called  "riser  vents"  and  take  the  form  shown  in  Fig.  88. 
The  valves  used  on  an  air-line  system  are  intended  to  close 
against  steam  only.  If  water  reaches  them  it  is  allowed  to  run 
into  the  air  lines,  from  which  it  is  drained  at  the  lowest  point. 
The  expansion  member  may  be  either  a  composition  post  or  a 
chamber  containing  a  volatile  liquid.  The  latter  type  is  coming 
into  general  use.  Fig.  89  illustrates  these  two  types. 


FIG.  89. — Air  line  valves. 

122.  Traps. — A  steam  trap  is  a  device  whose  function  is  to 
drain  the  water  from  a  steam  pipe,  separator,  or  radiator,  with- 
out allowing  steam  to  escape.  For  radiators,  special  traps  of  the 
float  or  thermostatic  form  described  in  Par.  103  are  used.  For 
draining  steam  lines  and  separators,  there  are  two  kinds  of  traps 
in  use,  designated  as  " float "  and  "bucket"  traps.  The  former 
consists  of  a  receiver  having  a  discharge  valve  controlled  by  a  float 
in  such  a  way  that  a  raising  of  the  water  level  from  an  influx  of 
water  causes  the  float  to  open  the  valve,  allowing  water  to  be 
discharged  by  the  pressure  of  the  steam  until  the  water  level  is 
lowered  to  its  normal  point.  One  design  of  float  trap  is  shown  in 
Fig.  90.  A  gage  glass  on  the  trap  indicates  the  water  level. 
There  is  normally  several  inches  of  water  above  the  valve  and  the 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  139 

existence  of  the  proper  water  level  affords  an  indication  that  the 
trap  is  operating  properly.  If  the  glass  is  empty,  the  trap  is 
allowing  steam  to  blow  through;  if  it  is  full,  the  trap  is  not 
adequately  taking  care  of  the  water. 

The  bucket  trap  consists  of  a  chamber  containing  a  bucket 
which  is  floated  by  the  water  in  the  chamber.  To  the  bucket 
are  attached  the  valve  stem  and  valve,  as  shown  in  Fig.  65.  The 
water  flowing  into  the  trap  enters  and  fills  the  bucket,  finally 
causing  it  to  sink  and  thereby  opening  the  discharge  valve. 
The  steam  pressure  forces  the  water  out  through  the  valve  and 
empties  the  bucket,  which  rises  and  closes  the  valve. 


FIG.  90. — Float  trap. 


FIG.  91. — Bucket  trap. 


It  is  possible  to  lift  the  condensation  by  means  of  a  trap  to  a 
height  approaching  that  equivalent  to  the  steam  pressure,  i.e., 
about  2.3  feet  per  pound  pressure.  It  is  better,  however,  if 
possible,  to  locate  the  trap  so  that  it  will  discharge  by  gravity. 

There  is  another  type  of  trap  which  is  used  where  large  quanti- 
ties of  water  must  be  handled.  This  is  the  tilting  trap,  one.  form 
of  which  is  shown  in  Fig.  92.  The  condensation  flows  by  gravity 
into  the  chamber  which  is  hinged  on  the  trunnions  A-A  and 
balanced  by  the  weight  B.  As  the  chamber  fills,  the  weight  B 
is  overbalanced  and  the  chamber  falls,  opening  the  discharge 
valve  C.  The  pressure  of  the  steam  forces  the  water  out  through 
the  discharge  valve  and  when  the  chamber  becomes  empty,  it 
tips  back  into  the  filling  position  and  the  discharge  valve  closes. 
The  tilting  trap  in  a  slightly  different  form  can  be  used  for  lifting 
the  condensation  from  low-pressure  piping  to  a  considerable 
height,  if  high-pressure  steam  is  available.  In  such  a  trap  an 


140 


HEATING  AND  VENTILATION 


additional  inlet  Valve  is  provided  for  the  high-pressure  steam, 
and  the  valves  are  so  arranged  that  when  the  chamber  fills  and 


Inlet 


FIG.  92.— Tilting  trap. 

drops,  the  main  inlet  valve  closes  and  the  high-pressure  inlet 
valve  opens,  admitting  high-pressure  steam  which  forces  out  the 
water  and  is  capable  of  raising  it  to  any  height  up  to  that  equiva- 
lent to  the  steam  pressure. 
Tilting  traps  are  sometimes 
very  useful  but  they  require 
considerable  attendance  in 
order  to  insure  their  reliable 
operation. 

123.  Separators.  —  The 
function  of  a  steam  separator 
is  to  remove  condensation 
from  steam  lines.  The  sepa- 
rator accomplishes  this  by 
abruptly  changing  the  direc- 
tion of  flow  of  the  steam  and 
SIDE  SECTION  END  SECTION  thereby  causing  the  entrained 

FIG.  93. — Steam  separator.  1,1  ,     , 

water  to  be  thrown  out,  by  its 

momentum,  against  a  suitably  designed  baffle,  usually  having 
a  series  of  grooves  which  conduct  the  water  into  a  receiver 


PIPE,  FITTINGS,  VALVES,  AND  ACCESSORIES  141 

below.  The  water  is  discharged  through  a  trap  or  seal.  This 
form  of  separator  is  illustrated  in  Fig.  93.  Separators  are 
placed  in  the  exhaust  line  from  pumps  and  reciprocating  engines, 
where  they  remove  the  oil  as  well  as  the  water  from  the  steam. 
In  choosing  a  separator  care  must  be  taken  to  select  a  size  cor- 
responding to  the  quantity  of  steam  flowing  rather  than  to  the 
size  of  the  pipe  line,  for  a  certain  velocity  through  the  separator 
is  necessary  to  insure  the  elimination  of  the  water. 


FIG.  94. — Reducing  valve. 

124.  Reducing  Valves. — Steam  is  occasionally  supplied  to  a 
building  at  a  pressure  much  higher  than  is  necessary  or  desirable 
for  heating  purposes,  making  it  necessary  to  employ  a  reducing 
valve,  a  simple  form  of  which  is  illustrated  in  Fig.  94.  The 
pressure  on  the  reduced  pressure  side  of  the  valve  is  transmitted 
through  the  balance  pipe  to  the  under  side  of  the  diaphragm, 


142  HEATING  AND  VENTILATION 

tending  to  close  the  valve.  The  force  thus  exerted  is  balanced  by 
that  due  to  the  weights  W-W  and  the  valve  will  assume  such 
a  position  that  just  enough  steam  will  pass  through  it  to  maintain 
the  required  pressure  on  the  reduced  side,  which  pressure  is 
governed  by  the  position  of  the  weights  on  the  lever  arm.  The 
reduced  pressure  may  be  changed  as  desired  by  shifting  these 
weights.  The  valve  shown  in  Fig.  94  is  double-seated,  so  that 
its  movement  is  independent  of  the  steam  pressure  on  either 
side  of  the  discs  and  is  controlled  solely  by  the  reduced  pressure 
acting  on  the  diaphragm.  Reducing  valves  should  be  installed 
with  a  bypass  so  that  they  can  be  removed  for  repairs  without 
interruption  of  the  steam  supply. 


CHAPTER  X 
STEAM  PIPING 

125.  General  Arrangement. — The  elementary  arrangement  of 
the  different  systems  of  steam  heating  was  shown  diagrammat- 
ically  in  Chapter  VIII.  Most  of  the  principles  involved  in  the 
design  of  the  piping  apply  equally  to  all  of  them. 


FIG.  95. — Single  pipe  up-feed  system. 

In  Fig.  95  is  shown  the  piping  for  a  single-pipe  upfeed  system. 
The  supply  mains  circle  the  basement,  pitching  away  from  the 
boiler,  and  are  dripped  at  the  ends  into  the  return  main.  For 

143 


144 


HEATING  AND  VENTILATION 


a  two-pipe  system,  the  return  mains  and  risers  would  be  arranged 
in  a  similar  manner. 


FIG.  96. — Overhead  vapor  or  vacuum  system. 

Fig.  96  shows  an  overhead  vapor  or  vacuum  system  in  a  tall 
building.     Return  risers  extend  from  the  top-floor  radiators  to 


STEAM  PIPING  145 

the  basement,  where  they  tie  into  the  main  return  line.  In 
large  buildings  the  first  floor  is  often  divided  into  small  stores 
which  require  heat  at  times  when  none  is  needed  in  the  remainder 
of  the  building  and  vice  versa,  making  it  desirable  to  install  a 
separate  main  to  supply  the  first-floor  radiators  and  arranged  so 
that  it  can  be  controlled  independently  of  the  main  heating 
system.  This  scheme  also  has  the  advantage  of  making  it 
much  easier  to  install  connections  to  the  first-floor  radiators 
which  are  often  so  located  that  it  is  difficult  to  reach  them  from 
the  risers.  In  extremely  tall  buildings  it  is  better  to  feed  the 
risers  from  the  bottom  as  well  as  from  the  top  and  a  supply 
main  is  installed  in  the  basement  for  that  purpose. 

126.  Principles  Involved  in  Piping  Design. — In  designing  and 
installing  a  system  of  piping,  attention  must  be  given  to  the 
following  fundamental  requirements: 

1.  Provision  for  expansion. 

2.  Proper  drainage  of  condensation  from  the  steam  lines. 

3.  Proper  arrangement  of  piping  and  use  of  pipes  of  the  proper 
size,  so  that  the  pressure  drop  due  to  friction  will  be  small. 

127.  Expansion. — Perhaps  the  most  important  consideration  is 
the  proper  provision  for  the  linear  expansion  of  the  pipes.     When 
steam  is  turned  into  or  shut  off  from  a  system  of  piping,  a  change 
of  temperature  of  the  pipe  amounting  to  from  140°  to  170°  takes 
place  and  provision  must  be  made  for  allowing  the  resulting 
change  of  length  to  occur  without  putting  excessive  strains  on  the 
fittings.     The  curve  in  Fig.  97  shows  the  theoretical  expansion  of 
wrought-iron  pipe  due  to  an  increase  in  temperature  from  60°  to 
the  temperature  corresponding  to  various  steam  pressures.     The 
temperature  of  60°  is  assumed  to  be  that  at  which  the  piping 
is  originally  installed.     For  low-pressure  piping  a  rough  rule  is 
to  allow  1J^  inches  of  expansion  per  100  feet  length  of  pipe. 

The  force  which  an  expanding  pipe  is  capable  of  exerting  is 
extremely  great.  If  constrained  at  the  ends  with  sufficient 
rigidity  the  increase  in  length  will  cause  the  line  to  "bow"  in 
the  center,  and  the  enormous  strain  thus  imposed  upon  the 
flanges  and  fittings  is  almost  certain  to  crack  them.  In  designing 
any  pipe  line  some  point  should  be  selected  as  a  fixed  or  anchored 
point  and  a  comprehensive  study  made  of  the  amount  and  direc- 
tion of  the  expansion.  Provision  must  be  made  for  properly 
taking  care  of  the  elongation  of  all  parts  of  the  system. 

There  are  in  general  three  ways  in  which  the  expansion  in  a 
10 


146 


HEATING  AND  VENTILATION 


system  of  piping  may  be  absorbed:  (a)  by  the  turning  of  some  of 
the  threaded  joints,  (b)  by  the  bending  of  the  pipes,  and  (c)  by  the 
use  of  special  devices  designed  to  absorb  the  movement. 

The  absorbing  of  the  expansive  movement  by  the  turning  of 
threaded  joints  is  permissible  only  in  low  pressure  piping  work. 
Continued  twisting  of  a  threaded  joint  will  in  time  often  result 
in  a  leak,  particularly  when  the  pressure  is  high.  In  heating 
work  it  is  common  practice  to  depend  upon  this  method  of  caring 
for  expansion.  In  many  cases  it  is  feasible  to  depend  upon  the 
bending  of  parts  of  the  piping,  and  this  is  usually  a  very  satis- 


2.0 


1.0 


20 


120 


140 


40  SO  80  100 

Steam  Pressure  -  Lbs.  per  Sq,  In.  Gage 

OcfeihaF  Temperature     60  ° 
FIG.  97. — Elongation  of  wrought  iron  pipe  with  various  steam  pressures. 

factory  method.  Examples  of  both  of  these  methods  will  be 
described  later.  For  extremely  large  or  long  pipes  it  is  some- 
times necessary  to  use  special  expansion  fittings. 

128.  Drainage. — There  is  always  some  water  in  pipes  carrying 
saturated  steam.  In  some  kinds  of  heating  systems,  in  addition 
to  the  condensation  formed  in  the  pipe  itself  there  is  also  con- 
densation from  other  parts  of  the  piping  and  from  the  radiators. 
The  proper  provision  for  the  flow  and  drainage  of  the  water  is 
important.  In  horizontal  pipes  the  water  should  if  possible  travel 
in  the  same  direction  as  the  steam  and  to  accomplish  this  the 
pipes  should  be  given  a  pitch  of  at  least  1  inch  in  10  feet  in  the 
direction  of  the  flow.  In  case  it  is  necessary  to  drain  the  con- 


STEAM  PIPING 


147 


densation  against  the  flow  of  the  steam,  as  in  a  branch  to  a  riser, 
a  much  greater  pitch  should  be  allowed  and  pipes  of  larger 
diameter  should  be  used  so  that  the  velocity  of  the  steam  will  be 
low.  Drainage  should  be  provided  for  any  necessary  pockets 
or  low  points  where  water  might  accumulate. 

129.  Mains  and  Branches. — Horizontal  mains  are  usually 
anchored  at  the  boiler  and  allowed  to  expand  freely  from  that 
point.  The  amount  of  movement  of  any  point  along  the  length 
of  the  pipe  is  evidently  proportional  to  its  distance  from  the 
fixed  point.  In  connecting  risers  and  branches  the  movement 
of  the  main  is  best  taken  care  of  by  either  of  the  arrangements 
in  Figs.  98  and  99.  As  the  main  moves  longitudinally  the 


FIG.  98.  FIG.  99. 

Methods  of  connecting  branches. 

threaded  joints  C-C  turn  slightly.  The  arrangement  of  Fig.  99 
is  somewhat  the  better  as  the  45-degree  elbow  offers  less  resistance 
to  the  flow  of  steam  than  the  90-degree  elbow  in  Fig.  98.  The 
expansion  of  the  horizontal  branch  is  taken  care  of  by  the  spring 
of  the  riser,  which  arrangement  is  quite  permissible  as  such 
branches  are  rarely  over  10  feet  long.  The  arrangement  shown 
in  Fig.  100  is  sometimes  used  when  the  expansion  of  the  main  is 
great.  It  has  the  disadvantage  of  offering  considerable  resis- 
tance to  the  flow  of  steam.  Branches  are  sometimes  taken  from 
the  bottom  of  the  main  as  in  Fig.  101.  It  is  then  necessary  to 
install  a  drip  connection  in  the  manner  shown.  This  arrange- 
ment is  undesirable  in  one  respect.  If  for  any  reason  the  water 
level  rises  in  the  return  system  above  the  horizontal  connection 
to  the  riser,  then  the  riser  will  be  entirely  sealed  from  the  main 


148 


HEATING  AND  VENTILATION 

The  one-pipe  relief  system 


and  its  steam  supply  will  be  cut  off. 
is  usually  piped  in  this  manner. 

In  very  long  horizontal  mains  in  which  the  movement  would 
be  too  great  to  be  absorbed  by  the  branch  connections  it  is  neces- 


Drip 


FIG.  100. 


FIG.  101. 


sary  to  anchor  the  pipe  at  two  or  more  points  and  to  provide  a 
swivel  joint  of  the  form  shown  in  Fig.  102.  One  objection  to  this 
method  is  the  resistance  to  the  flow  of  steam  offered  by  the 
fittings. 


FIG.  102. — Expansion  swivel. 


FIG.   103. 


Another  scheme  which  is  sometimes  used  where  the  main 
makes  a  turn  of  90  degrees  is  that  shown  in  Fig.  103.  With  this 
arrangement  the  expansion  is  largely  absorbed  by  the  spring  of 
the  members. 


FIG.  104. 


FIG.  105. 


When  the  size  of  the  main  is  reduced  an  eccentric  reducer 
should  be  used  as  in  Fig.  105  so  that  no  water  pocket  will  be 
formed.  The  accumulation  of  water  in  shallow  pockets  such  as 


STEAM  PIPING 


149 


that  formed  by  the  reducing  tee  in  Fig.  104  gives  rise  to  severe 
cracking  and  pounding  when  the  heating  system  is  started  up. 

130.  Risers. — In  small  buildings  where  the  supply  mains  are 
in  the  basement,  the  expansion  of  the  risers  is  usually  downward 
and  the  movement  is  taken  care  of  by  the  spring  of  the  branches 
(see  Figs.  98  and  99).  In  larger  buildings,  where  there  is  a  main 
in  the  attic,  the  risers  are  anchored  near  the  middle  and  the 
expansion  takes  place  in  both  directions.  When  the  expansion  is 
too  great  to  be  handled  by  an  ordinary  branch  connection  the 
arrangement  in  Fig.  106  may  be  used.  This  gives  a  perfect  swivel 
joint  and  is  especially  serviceable  when  the  basement  main  must 


FIG.    106. — Flexible    connection   for 
riser. 


FIG.  107. — Expansion  loop 
for  riser. 


be  installed  near  the  foot  of  the  risers.  Its  disadvantage  is  the 
resistance  to  the  steam  flow  offered  by  the  fittings. 

The  branch  connection  shown  in  Fig.  99  will  easily  take  care 
of  the  expansion  of  risers  about  four  stories  high,  and  that  in 
Fig.  106  about  eight  stories.  For  taller  buildings  an  expansion 
loop  of  the  form  shown  in  Fig.  107  is  installed  in  the  middle  of 
each  riser.  Such  an  expansion  loop  is  easily  capable  of  handling  a 
length  of  riser  of  at  least  four  stories  in  either  direction  and  gives 
perfect  flexibility.  Space  is  required  in  the  furring  to  conceal 
the  loop. 

131.  Drip  Connections  and  Air  Venting. — The  ends  of  mains 
are  dripped  in  the  manner  shown  in  Fig.  108.  An  air  valve  should 
be  installed  at  such  points  to  free  the  main  of  air  when  the  system 
is  started  up.  Drips  from  different  mains  should  not  be  con- 


150 


HEATING  AND  VENTILATION 


Last  Brunch 
Connection  - 


Main 


Valvp 


nected  together  above  the  water  line  as  the  pressure  of  the  steam 
in  them  may  be  different,  in  which  case  the  flow  of  the  condensa- 
tion would  be  interfered  with  and  a  water-hammerset  up. 

Air  vents  should  be 
located  at  the  ends  of  all 
mains  and  at  other  places 
where  air  is  liable  to 
become  pocketed. 

132.  Pipe  Hangers. — 
The  piping  in  a  heating 
system  must  be  substan- 
tially supported  either 
from  the  building  struc- 
ture or  from  special  sup- 
ports. Horizontal  mains 


Orip 


FIG.  108. — Drip  at  end  of  main. 


are  usually  hung  from  the  joists  or  steel  work  of  the  floor  above. 
For  pipes  of  moderate  size  the  hanger  shown  in  Fig.  109  is  widely 
used.  The  perforated  metal  can  be  obtained  in  strips  and  cut 
to  any  required  length.  This  hanger  is  of  low  cost  and  can  be 
installed  very  cheaply. 


FIG.  109. — Simple  form  of  pipe  hanger. 

For  heavier  pipes  the  hanger  shown  in  Fig.  110  is  a  common 
design.  The  turnbuckle  is  used  to  adjust  the  elevation  of  the 
pipe  when  it  is  being  installed.  Both  of  these  hangers  permit 


STEAM  PIPING 


151 


the  free  longitudinal  movement  of  the  pipe  line.     Hangers  should 
be  placed  at  intervals  of  20  feet  or  less  on  all  horizontal  pipes. 


FIG.  110. — Hanger  for  large  pipes.1 


PLAN 

FIG.  111. — Anchor  for  riser.1 


Risers  are  supported  at  the  anchor  points  in  some  such  manner 
as  is  illustrated  in  Fig.  111. 

From  "  Pipe-fitting  Charts"  by  W.  G.  SNOW. 


152 


HEATING  AND  VENTILATION 


133.  Return  Piping. — Return  pipes  of  any  kind  of  a  steam 
system  should  be  designed  with  ample  provision  for  expansion 
as  they  may  at  times  be  heated  to  steam  temperatures.  Dry- 
return  mains  should  be  given  a  pitch  of  at  least  1  inch  in  10  feet 
toward  the  boiler.  Wet  return  mains  should  also  be  pitched 
toward  the  boiler  so  that  they  may  be  entirely  drained  of 
water  when  necessary.  Return  pipes  should  never  be  buried 
in  the  ground  without  protection.  When  it  is  necessary  to  con- 
ceal them  the  best  plan  is  to  arrange  them  in  trenches  with  remov- 
able cover  plates.  An  alternate  scheme  is  to  cover  them  with 
cylindrical  tile  with  cemented  joints  which  will  keep  out  the 


FIG.   112. — Water  level  in  return  line  of  vapor  system. 

water.     When  buried  in  soil,  return  pipes  corrode  and  deteriorate 
very  rapidly. 

134.  Vapor  and  Vacuum  Systems. — In  a  vapor  system,  since 
the  return  lines  are  under  atmospheric  pressure,  the  water  will 
build  up  in  the  return  leg  (Fig.  112)  to  a  height  above  that  in  the 
boiler  equivalent  to  the  pressure  in  the  boiler.  In  order  to  pre- 
vent the  return  mains  from  becoming  flooded  the  distance  from 
the  water  line  of  the  boiler  to  the  horizontal  return  main,  desig- 
nated by  h  in  Fig.  112,  should  be  as  great  as  possible  and  should 
never  be  less  than  2J^  feet.  In  some  cases  it  is  necessary  to 
place  the  boiler  in  a  pit  below  the  basement  floor,  in  order  to 
accomplish  this.  The  supply  main  of  a  vapor  system  can  often 


STEAM  PIPING 


153 


be  dripped  at  the  end  into  the  return  main  through  a  thermo- 
static  trap.  This,  however,  necessitates  starting  the  return 
main  at  an  elevation  below  the  end  of  the  supply  main  which, 
with  the  necessary  pitch  toward  the  boiler,  may  bring  it  very 
close  to  the  water  line.  A  better  arrangement  is  to  install  a 
separate  drip  line  from  the  end  of  the  supply  main,  which  allows 
the  return  main  to  be  placed  much  higher.  This  arrangement 


Drip  from 
End  of 


FIG.  113. — Method  of  dripping  supply  main  when  basement  is  shallow. 

is  shown  in  Fig.  113,  the  dotted  line  representing  the  necessary 
elevation  of  the  return  main  if  the  drip  line  is  omitted. 

In  an  overhead  vapor  or  vacuum  system  each  riser  is  dripped 
at  the  bottom  through  a  thermostatic  trap  as  in  Fig.  114.  In 
order  to  catch  the  dirt  and  scale  which  would  clog  the  trap  a  dirt 
pocket  should  be  provided,  consisting  of  a  short  capped  pipe. 
Steam  mains  are  dripped  into  the  return  line  in  a  similar  manner. 


XI 
Kiser 


Trap 


Dirt  Pocket 


Return  Main' 
FIG.  114. — Drip  connection  to  riser  in  a  vapor  or  vacuum  system. 

Bypasses  are  sometimes  provided  for  the  most  important  traps 
to  enable  them  to  be  easily  cleaned  or  inspected  and  dirt  strainers 
are  also  sometimes  used. 

135.  Valves. — The  location  of  valves  in  a  heating  system 
should  be  given  careful  consideration.  While  valves  are  desirable 
in  many  locations,  there  are  also  some  places  where  they  should 
never  be  installed  unless  the  plant  is  in  the  hands  of  a  competent 


154 


HEATING  AND  VENTILATION 


engineer,  because  of  the  possibility  of  accidents  resulting  from 
ignorant  handling  of  them. 

In  a  small  system  as  few  valves  should  be  installed  as  possible. 
Indeed  for  residence  systems  it  is  seldom  necessary  to  install  any 
valves  except  at  the  radiators.  Valves  should  never  be  installed 
on  the  steam  outlet  of  the  boiler  or  on  the  return  connection 
unless  the  plant  is  under  careful  supervision  or  unless  two  boilers 
are  used  in  parallel,  in  which  case  valves  are  necessary  in  order 
to  enable  one  boiler  to  be  cut  out  of  service  for  repairs. 

In  large  buildings  a  valve  should  be  provided  on  each  riser, 
if  possible,  so  that  a  riser  can  be  shut  off  for  repairs,  etc., 
without  necessitating  the  shutting  down  of  the  entire  system. 
Valves  should  also  be  provided  on  each  branch  main  and  return 
line  in  such  buildings.  Gate  or  angle  valves  should  be  used  in 
preference  to  globe  valves. 

136.  Radiator  Connections. — The  connections  to  a  radiator 
must  be  sufficiently  flexible  so  that  the  main  or  riser  is  perfectly 


FIG.    115.  —  Connection   to 
first  floor  radiator. 


FIG.   116. — Connections  from  risers  where  ver- 
tical movement  is  small. 


free  to  expand  without  straining  the  fittings.  They  must  also 
be  designed  to  allow  the  radiator  to  drain  properly  and  must 
be  free  from  water  pockets.  Figs.  115,  116,  and  117  show  some 
proper  methods  of  connecting  radiators  in  a  single-pipe  system. 
That  shown  in  Fig.  115  is  used  for  first-floor  radiators  connected 
directly  to  the  main.  The  connection  in  Fig.  116  is  suitable  for 
risers  whose  vertical  movement  is  small  enough  to  be  absorbed 
by  the  spring  of  the  horizontal  pipe.  An  objection  to  this 
arrangement  is  the  fact  that  the  connection  is  under  the  floor  and 
inaccessible  unless  the  horizontal  branch  is  exposed  in  the  room 


STEAM  PIPING 


155 


below  as  shown  by  the  dotted  lines.     In  the  connection  shown  in 
Fig.  117  a  radiator  valve  of  the  " corner"  pattern  is  used  and  the 


FIG.  117. — Flexible  connection,  plan  view — used  when  riser  has  considerable 

vertical  movement. 

use  of  the  elbows  gives  a  very  flexible  combination  which  is  well 
suited  for  tall  buildings  where  the  movement  of  the  risers  is 
considerable. 


FIG.  118. — Radiator  connections — vapor  system. 

The  connections  to  a  radiator  of  a  vapor  system  are  shown  in 
Fig.  118.  These  connections  are  also  very  flexible  and  the  use 
of  45-degree  elbows  reduces  the  frictional  resistance. 


U 


FIG.  119. — Wrong  method. 

In  no  case  should  a  radiator  be  connected  as  in  Fig.  119.  The 
short,  stiff  connection  allows  no  free  vertical  movement  of  the 
riser  and  causes  severe  strains  on  the  fittings. 


156 


HEATING  AND  VENTILATION 


137.  Pipe  Coils. — Pipe  coils  may  be  connected  in  the  manner 
shown  in  Figs.  120a  and  1206.  The  arrangement  in  Fig.  120a  is 
used  for  a  two-pipe  system  and  that  in  Fig.  1206  for  a  single-pipe 
system.  A  return  connection  is  always  used  on  pipe  coils 
because  of  the  difficulty  of  draining  the  large  amount  of  condensa- 


FIG.   120a. 


FIG.   1206. 


Methods  of  connecting  pipe  coils. 

tion  formed  in  radiation  of  this  type  back  through  the  inlet 
connection.  The  check  valve  in  Fig.  1206  prevents  steam  from 
entering  the  coil  through  the  return  connection.  In  order  to 
open  the  check  valve  against  the  pressure  of  the  steam  in  the 
riser  a  water  head  must  be  built  up  above  it  equivalent  to  the 
drop  in  pressure  through  the  coil,  which  may  be  quite  appreciable. 
Therefore,  a  short  length  of  vertical  pipe  should  be  installed 
above  the  check  valve  as  shown,  to  receive  the  water  column 
which  would  otherwise  occupy  the  lower  part  of  the  pipe  coil. 


Steam  Main 


Return  Aiain 


FIG.  121.' — Boiler  connections. 


138.  Boiler  Connections. — The  usual  method  of  arranging 
the  connections  to  a  steam  boiler  is  shown  in  Fig.  121.  In 
addition  to  the  supply  and  return  connections  there  is  required 
a  blow-off  cock  and  a  city  water  connection  with  a  shut-off  valve 


STEAM  PIPING  157 

and  a  check  valve.  It  is  sometimes  necessary  to  connect  two 
boilers  in  parallel.  This  must  be  carefully  done  so  that  there 
will  be  no  chance  of  either  boiler  losing  water  to  the  other. 
Connections  of  ample  size  between  both  steam  and  return 
connections  should  be  made  so  that  the  pressure  and  water 
levels  in  both  boilers  will  be  always  the  same. 

139.  Flow  of  Steam  in  Pipes. — When  any  fluid  flows  through 
a  pipe  a  certain  pressure  is  necessary  to  move  it  against  the 
resistance  caused  by  the  friction  of  the  fluid  against  the  inner 
surface  of  the  pipe.  The  following  laws  governing  the  friction 
of  fluids  in  pipes  have  been  established  by  experiment: 

1.  The  total  amount  of  frictional  resistance  is  independent  of  the 
absolute  pressure  of  the  fluid  against  the  pipe  wall. 

2.  The  frictional  resistance  varies  nearly  as  the  square  of  the 
velocity. 

3.  The  frictional  resistance  varies  directly  as  the  area  of  contact 
between  the  fluid  and  the  pipe  wall. 

4.  The  frictional  resistance  varies  directly  as  the  density  of  the 
fluid. 

Consider  a  condition  of  steady  flow  in  a  pipe  and  let  pi  (Fig. 
122)  be  the  unit  static  pressure  of  the  fluid,  at  one  point  and 


FIG.   122. 

let  pz  be  the  pressure  at  another  point  at  a  distance  L  from  the 
first.  The  drop  in  pressure  due  to  the  friction  of  the  fluid  in 
passing  through  the  distance  L  is  then 

P  =  Pi-  P2 

Expressing   the   laws   of  friction   stated   above   in   algebraic 
form  we  have 

Pa  =  FSDv2  (1) 

in  which 

P  =  drop  in  unit  pressure  in  pounds  per  square  foot. 
a  =  cross-sectional  area  of  the  pipe  in  square  feet. 
F  =  a  constant  depending  on  the  nature  of  the  fluid  and 

the  nature  of  the  pipe  surface. 
S  =  area  of  contact  between  the  fluid  and  the  pipe  in 

square  feet. 

D  =  density  of  the  fluid  in  pounds  per  cubic  foot. 
v  =  velocity  of  the  flow  in  feet  per  second. 


158  HEATING  AND  VENTILATION 

Then  P  =  ^FSDv*  (2) 

Let  F  be  made  arbitrarily  =  ^ 

Then  equation  (2)  becomes 

1         v2 

P  =  -fSD^  (3) 

a         2g 

v* 
This  is  done  simply  to  bring  into  the  expression  the  term  5- 

which  is  the  usual  form  for  expressions  of  this  nature. 
For  round  pipes  of  diameter  d  and  length  L,  S  =  irdL  and  a  = 

4' 

Then  P  = 

Let     w  =  the  weight  of  steam  flowing  in  pounds  per  minute. 
Then  w  =  ^XvXDXQO  =  47.l2d2vD 

and  v  =  4fr  10  ,9-7v  (5) 


p 
Let  p  be  the  pressure  drop  in  pounds  per  square  inch  =  JT^  and 

let  di  be  the  diameter  in  inches  -  12d. 

Substituting  in  (4)  these  values  for  v,  P  and  d  we  have 

p=  0.04839  ^5  (6) 

The  coefficient  /  was  found  by  Unwin  to  be  =  K  (l  -f  YTJJ) 


The  value  most  commonly  used  for  X  for  steam  is  that  de 
termined  by  Babcock  which  =  0.0027. 
Substituting  in  (6)  we  have 

p  =  0.0001306  w2L(l  +  ~> 


in  which 

p  =  pressure  drop  in  pounds  per  square  inch. 

w  =  weight  of  steam  flowing  in  pounds  per  minute. 

L  =  length  of  pipe  in  feet. 

di  =  diameter  of  pipe  in  inches. 

D  =  average  density  of  steam  in  pounds  per  cubic  foot. 


STEAM  PIPING  159 

The  value  of  the  coefficient  /  given  above  has  been  found  to 
be  correct  for  small  pipes  and  comparatively  low  velocities, 
For  large  pipes  and  high  velocities  the  value  of  /  is  considerably 
lower.1 

140.  Factors  Affecting  the  Size  of  Pipes. — The  sizes  of  pipes 
to  be  used  in  a  heating  system  depend  upon  several  factors. 
The  fundamental  requirement  as  regards  the  supply  pipes  is 
that  they  must  be  of  sufficient  capacity  to  transmit  the  required 
quantities  of  steam  with  the  pressure  differential  which  is  avail- 
able. The  latter  depends  somewhat  upon  the  source  of  the 
steam  supply.  When  exhaust  steam  from  an  engine  or  turbine 
is  used  for  heating,  it  is  best,  from  the  standpoint  of  economy, 
to  make  possible  the  carrying  of  a  low  back-pressure  by  designing 
the  heating  system  to  operate  with  an  initial  pressure  of  not 
over  2  pounds  per  square  inch.  The  same  practice  should  usually 
be  followed  when  steam  is  taken  direct  from  a  boiler,  as  it  may 
be  desired  at  some  future  time  to  use  exhaust  steam.  The 
circulation  will  also  be  much  better  and  the  system  more 
satisfactory  if  the  pipe  sizes  are  ample.  When  a  vacuum  pump 
is  used  the  greater  pressure  differential  thus  set  up  makes  possible 
the  use  of  smaller  pipes  but  it  is  well,  nevertheless,  to  design  the 
supply  piping  to  operate  as  a  gravity  system  with  a  moderate 
pressure  drop  so  that  the  pump  can  be  shut  down  at  times  if 
desired.  The  return  pipes,  however,  can  be  made  somewhat 
smaller  if  a  vacuum  pump  is  to  be  used. 

Another  factor  which  makes  an  extreme  reduction  in  the  size 
of  the  supply  pipes  undesirable  is  the  noise  caused  by  the  result- 
ing high  velocity  of  the  steam  flowing  through  them.  On  the 
other  hand,  to  make  the  pipes  of  excessive  size  increases  unneces- 
sarily the  cost  of  the  system.  Because  of  these  various  factors 
it  is  common  practice  to  take  as  a  safe  standard  for  the  rate  of 
pressure  drop  in  the  supply  piping  a  drop  of  from  0.03  to  0.10 
pounds  per  100  feet  of  pipe. 

There  are  other  factors  beside  that  of  pressure  drop  which 
affect  the  size  of  the  supply  pipes,  such  as  the  provision  for  the 
carrying  of  condensation.  In  general  all  steam  pipes  in  which 
the  condensation  drains  in  the  opposite  direction  to  the  flow  of 
steam  should  be  larger  than  if  both  flow  in  the  same  direction. 

1  See  "The  Transmission  of  Steam  in  a  Central  Heating  System"  by 
J.  H.  WALKER,  Trans.  A.  S.  H.  &  V.  E.,  1917. 


160  HEATING  AND  VENTILATION 

This  applies  particularly  to  single-pipe  radiator  connections 
and  branches  and  to  the  risers  of  single-pipe  systems. 

The  proper  size  of  return  pipes  is  based  upon  experience  and 
good  practice  as  there  is  no  definite  law  upon  which  their  size 
can  be  computed.  They  must  first  of  all  be  sufficiently  large 
to  carry  the  condensation.  Second,  they  srioji]iLbeJarge  enough 
so  that  they  will  not  become  plugfedwith  dirt ;  and  third,  they 
musl,  inji  vapor  or  vacuum  system,  be  large  enough  to"liandle 
the  air  from  the  radiators  as  well  as  the  condensation,  when  the 
radiators  are  first  turned  on. 

141.  Selection  of  Sizes  of  Supply  Pipes. — In  a  large  or  impor- 
tant system  it  is  very  desirable  to  make  a  detailed  calculation  of 
the  pressure  drop  through  the  system.  Besides  insuring  ample 
pipe  sizes  this  will  enable  the  pipe  sizes  to  be  reduced  in  some 
cases  below  those  which  would  be  chosen  arbitrarily.  In  a  large 
building  a  considerable  saving  may  be  effected  by  judiciously 
choosing  the  pipe  sizes  for  the  risers  and  mains.  In  a  system  in 
which  the  supply  to  individual  radiators  is  controlled  by  gradu- 
ated valves  it  is  very  desirable  to  have  approximately  the  same 
pressure  at  all  radiator  valves.  To  accomplish  this  fully  would 
be  an  impossibility,  but  such  a  condition  can  be  approximated 
by  careful  design. 

In  selecting  the  pipe  sizes,  the  desired  pressure  drop  through 
the  system  is  chosen  and  the  approximate  average  drop  per  unit 
length  of  pipe  is  found,  after  which  the  exact  drop  can  be  com- 
puted by  means  of  formula  (7),  Par.  139.  In  order  to  facilitate 
the  calculations,  the  chart  in  Fig.  123  may  be  used  and  the 
pressure  drop  per  10  feet  of  pipe  read  directly.  The  chart  is 
based  on  an  average  density  of  the  steam  corresponding  to  a 
pressure  of  2  pounds  gage,  which  is  sufficiently  accurate  for  the 
range  of  pressure  which  occurs  in  a  heating  system.  In  figuring 
the  capacities  of  the  pipes  no  allowance  need  be  made  for  con- 
densation in  the  pipes  themselves  as  this  will  ordinarily  be  negli- 
gible if  the  pipes  are  covered,  but  if  the  pipes  are  to  be  left  bare 
their  radiating  surface  should  be  included  with  that  of  the 
radiators.  The  scales  at  the  bottom  of  the  sheet  read  directly 
in  square  feet  of  radiation  having  an  assumed  heat  transmission 
of  245  B.t.u.  per  square  foot  per  hour,  which  is  the  amount 
which  would  be  transmitted  from  38-inch,  two-column  radia- 
tion with  a  room  temperature  of  70°  and  a  'steam  temperature 
corresponding  to  the  pressure  of  2  pounds.  The  scales  at  the 


STEAM  PIPING 


161 


top  of  the  sheet  read  in  B.t.u.  delivered  per  hour,  and  are  con- 
venient for  use  when  the  B.t.u.  to  be  delivered  by  each  radiator 
is  known.  As  an  example  of  the  use  of  the  chart,  consider  a 
riser  218  feet  long  supplying  3000  square  feet  of  radiation.  If 
the  drop  through  the  riser  is  to  be  not  more  than  0.1  pound, 
find  the  proper  pipe  size.  The  drop  of  0.1  pound  in  218  feet  is 


Use  upper  scale  for  pipe  siz 

2,000   3,000  4,000 
20      30    40 


es  5"and  over    Heat  Delivered  per  Hour  Thousands  of  B.t.u.  a. 

6,000    8,000   10,000  20,000  40,000     60.00080,000100,000  200,000 

50    60    708090100  200  300      400    500600      800     1,000  2,000 


.10 

.09 
.08 
.07 
.06 
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Steam  Pressure    Slbs.ga 
Steam  Temp.         218.5  de 
at  Transmission  of  Radial 
245  B.t.u  .per  sq.ft.perh 

/       / 

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50    60708090100  200  300      400     500600     800    1,000 

6,000  10,000  20,000   30,000  40,000      60,00080,000100,000 

TJie  l<mer  scale  for  pipe  sizes  6'W  over         Radiation   Sq.  Ft. 

FIG.  123. 


2,000 
200,000 


3,000  4,000 
300,000 


6,000  8,000  10,000) 


equivalent  to  a  drop  of  0.0046  pound  in  10  feet.  Passing  ver- 
tically from  the  3000-square  feet  point  on  the  horizontal  scale 
to  intersect  the  diagonal  lines  for  the  4-inch  and  5-inch  pipes 
we  see  that  a  5-inch  pipe  will  transmit  the  steam  with  a  drop 
of  0.0026  pound  in  10  feet  and  the  4-inch  pipe  with  a  drop  of 
0.0089  pound  in  10  feet,  which  indicates  that  the  5-inch  pipe 

is  the  proper  size. 

11 


162 


HEATING  AND  VENTILATION 


The  frictional  resistance  of  the  fittings  must  also  be  considered. 
It  is  customary  to  reduce  these  resistances  to  equivalent  lengths 
of  straight  pipe,  to  be  added  to  the  actual  length,  according 
to  Table  XXVIII. 

TABLE  XXVIII. — EQUIVALENT  RESISTANCE  OF  FITTINGS 


Fitting 

Equivalent  length  of 
straight  pipe  expressed  in 
no.  of  pipe  diameters 

90-degree  elbow 

40 

45-degree  elbow  

20 

Tee  

40 

Reducing  coupling 

40 

Valve 

60 

142.  Example  of  Method  of  Computing  Pipe  Sizes. — Consider 
the  overhead  vapor  system  shown  diagrammatically  in  Fig.  124, 
and  let  it  be  required  to  choose  the  pipe  sizes  so  that  the  pressure 
drop  through  the  system  will  be  between  0.3  and  0.5  pound. 
The  equivalent  lengths  of  the  sections  of  pipe  should  first  be 


Main  Riser 


Boiler 


computed  and  set  down  in  tabular  form.  Assuming  a  pressure 
of  2  pounds  at  the  boiler,  the  pressure  drop  through  each  section 
of  the  main  and  the  riser  h-p,  the  longest  path  of  the  steam  flow, 
is  computed.  The  total  length  of  the  path  being  387  feet,  the 
average  pressure  drop  may  be  taken  as  0.4  -f-  38.7  =  0.010  pound 


STEAM  PIPING 


163 


per  10  feet  of  pipe.  The  pressure  drop  through  each  of  the 
successive  sections  may  then  be  computed  from  the  chart  in 
Fig.  123,  using  the  pipe  sizes  which  will  give  as  nearly  as  possible 
the  average  pressure  drop  determined  above.  The  results  may 
be  arranged  in  tabular  form  as  in  Table  XXIX. 

TABLE  XXIX 


Section 

Equivalent 
length,  ft. 

Rad. 
supplied 

Initial 
pressure 

Pipe 
size 

Pressure  drop  in  section 

a—b 

130 

17,120 

2.000 

8 

0.0075X13.0  =  0.0974 

b-c 

20 

10,700 

1.903 

6 

0.0125X  2.0  =  0.0250 

c-d 

23 

9,090 

1.878 

6 

0.0090X  2.3=0.0210 

d-e 

19 

7,290 

1.857 

5 

0.0150X   1.9  =  0.0290 

e-f 

27 

5,510 

1.828 

5 

0.0090X  2.7  =  0.0240 

f-9 

23 

3,660 

1.804 

4 

0.0130X  2.3  =  0.0300 

g-h 

25 

,960 

1.774 

3 

0.0170X  2.5  =  0.0420 

h-i 

15 

,960 

1.732 

3 

0.0170X  1.5  =  0.0250 

i-j 

15 

,700 

1.707 

3 

0.0130X  1.5  =  0.0190 

j-k 

15 

,460 

.688 

3 

0.0090X  1.5  =  0.0140 

k-l 

15 

,220 

.674 

2^ 

0.0220X  1.5  =  0.0330 

l-m 

15 

980 

.641 

2M 

0.0140X   1.5  =  0.0210 

m-n 

15 

740 

.620 

2 

0.0220X  1.5  =  0.0330 

n-o 

15 

500 

.587 

2 

0.0100X   1.5=0.0150 

o-p 

15 

260 

.572 

1H 

0.0110X  1.5=0.0160 

387 

Final  pressure  at  p  =  1.556  pound. 
Total  drop  =  0.444  pound. 

In  systems  of  this  kind  it  is  desirable  to  have  about  the  same 
pressure  at  all  of  the  lowest  radiators.  The  other  risers,  there- 
fore, can  be  designed  for  such  a  pressure  drop  that  the  pressure 
at  the  bottom  of  each  will  be  approximately  1.556  pound. 

143.  Approximate  Method. — While  the  method  outlined  in  the 
preceding  paragraphs  should  be  used  for  large  or  important 
installations,  it  is  quite  sufficient  for  many  cases,  to  choose 
the  pipe  sizes  simply  from  the  amount  of  radiation  supplied. 
In  Table  XXX  are  given  sizes  of  mains  and  return  lines  for 
various  amounts  of  radiation  for  all  classes  of  systems. 

144.  Radiator  Connections. — In  order  to  allow  the  condensa- 
tion to  drain  out  against  the  inflowing  steam  the  connections  to 
radiators  of  one-pipe  systems  should  be  of  ample  size  and  the 
size  of  the  nearly  horizontal  branches  should  be  still  more  gener- 


164 


HEATING  AND  VENTILATION 


ously  proportioned.  In  two-pipe  systems  the  radiator  supply 
connections  carry  little  condensation  and  may  therefore  be  rela- 
tively small.  The  sizes  of  connections  commonly  used  for  radia- 
tors of  various  capacities  are  given  in  Table  XXXI. 

TABLE    XXX. — PIPE  SIZES  FOR  SUPPLY  AND  RETURN  LINES 


Pipe  size 

M 

H 

1 

IK 

1H 

2 

2H 

3 

m 

Supply     mains  —  all     systems 

50 

100 

175 

350 

600 

1  000 

1  500 

Upfeed  risers*  —  one-pipe  sys- 
tem                                     

• 

50 

100 

200 

300 

500 

700 

Dry     return     lines  —  two-pipe 
and  vapor  systems  
Wet  return  lines  .        

50 

150 
2,000 

300 
3,800 

900 
6,000 

2,000 
13,000 

3,800 
23,000 

6,000 
37,000 

10,000 
55,000 

Vacuum  return  lines  

100 

400 

800 

1,500 

3,000 

6,000 

10,000 

18,000 

30,000 

Pipe  size 

4 

5 

G 

8 

10 

12 

14 

16 

Supply      mains  —  all     systems 

downfeed  risers,  all  systems  .  . 

2,000 

3,800 

6,000 

13,000 

23,000 

35,000 

55,000 

78,000 

Upfeed  risers*  —  one-pipe  sys- 

800 

1,300 

1,800 

3,000 

Dry     return     lines  —  two-pipe 

13,000 

23  000 

37,000 

78,000 

Wet  return  lines 

78,000 

• 

Vacuum  return  lines  

40,000 

65,000 

*  Which  carry  condensation  from  radiators. 

TABLE  XXXI. — SIZE  OF  RADIATOR  CONNECTIONS 


One-pipe  radiators 


Two-pipe  radiators 


Size  of 
radiator, 
square  feet 

'  Radiator 
connection 

Horizontal 
branch 

Size  of 
radiator, 
square  feet 

Size  of 
supply 
connection 

Size  of 
return 
connection 

20 

1 

1 

48 

1 

X 

24 

1 

IX 

96 

IK 

1 

40 

IX 

iX 

over  96 

IX 

IX 

60 

IX 

IX 

80 

IX 

ix 

100 

IK 

2 

200 

2 

2 

The  size  of  pipe  actually  required  to  convey  the  necessary 
amount  of  steam  is  usually  considerably  less  than  these  arbitrary 
sizes. 


STEAM  PIPING  165 

145.  Erection  and  Installation  of  Piping.— It  is  very  necessary 
that  the  installation  of  a  heating  system  be  supervised  carefully, 
as  an  immense  amount  of  trouble  can  be  caused  by  careless 
workmanship. 

One  of  the  most  important  points  is  the  proper  threading  and 
making  up  of  the  pipe  joints.  Sharp  clean  threads  of  the  proper 
length  should  be  the  aim,  the  cutting  of  which  requires  that  the 
threading  dies  be  kept  in  perfect  condition.  In  making  up  the 
joints  the  threads  should  be  wiped  perfectly  clean  and  coated 
with  a  very  small  amount  of  pipe-joint  compound.  The  use 
of  too  great  a  quantity  of  compound  is  a  frequent  and  a  serious 
mistake  as  the  substance  clogs  the  traps,  valves,  and  return  lines 
and  is  a  continual  source  of  trouble. 

Pipes  of  the  3-inch  size  and  under  are  cut  with  a  hand  cutter 
which  leaves  a  burr  on  the  inside  of  the  pipe.  In  the  smaller 
pipes,  especially,  a  considerable  reduction  in  the  internal  diam- 
eter may  thus  be  produced  and  the  burr  should  therefore  be 
removed  with  a  reamer. 

The  piping  should  be  uniformly  pitched  and  all  air  or  water 
pockets  should  be  avoided.  Hangers  should  be  installed  in 
sufficient  numbers  and  in  proper  locations  so  that  no  strains 
on  fittings,  valves,  or  boiler  connections  will  be  caused  by  the 
weight  of  the  piping. 

One  common  source  of  trouble  especially  in  new  installations 
is  the  dirt  which  gets  into  the  piping  while  it  is  being  installed. 
This  dirt,  consisting  of  cement,  plaster,  chips,  etc.  from  the  build- 
ing operations,  and  chips  produced  in  threading  the  pipe,  causes 
a  great  deal  of  damage  in  clogging  the  pipes,  traps,  and  fittings 
and  in  cutting  out  the  valve  seats  and  discs.  Most  important 
of  all,  the  open  ends  of  the  piping  during  installation  should  be 
kept  carefully  covered  to  prevent  dirt  from  entering.  Systems 
having  traps  on  the  radiators  should  be  operated  for  a  week  or  two 
without  the  traps  so  that  most  of  the  dirt  will  be  washed  out 
before  the  traps  are  installed. 

146.  Heating  Systems  in  Connection  with  Power  Plants. — 
In  designing  the  piping  for  a  heating  system  to  be  operated  in 
conjunction  with  a  power  plant,  provision  must  be  made,  first,  to 
use  the  exhaust  steam  for  heating,  with  a  means  for  allowing  the 
excess   exhaust   to   escape    automatically   to    atmosphere,    and 
second,  to  supply  live  steam  to  the  heating  system  during  the 
hours  when  the  heating  requirements  are  in  excess  of  the  amount 


166 


HEATING  AND  VENTILATION 


of  exhaust  steam  available.     A  common  arrangement  is  that 
shown  in  Fig.  125.     The  back-pressure  valve,  located  on  the 


main  exhaust  line,  is  so  constructed  that  an  increase  of  pressure 
over  the  amount  for  which  the  valve  is  set  causes  it  to  open  and 


STEAM  PIPING  167 

discharge  steam  to  the  atmosphere.  The  condensation  from  the 
radiators  is  discharged  by  the  vacuum  pump  to  the  open  feed- 
water  heater  from  which  it  is  taken  by  the  boiler  feed  pump.  A 
pressure-reducing  valve  with  a  bypass  is  used  to  feed  steam  direct 
from  the  boilers  into  the  heating  system  when  required.  The 
reducing  valve  may  be  set  to  open  when  the  pressure  in  the  heat- 
ing system,  because  of  an  insufficiency  of  the  exhaust  steam 
supply,  drops  below  the  required  point.  The  exhaust  steam  from 
the  pumps  is  discharged  into  the  main  exhaust  line,  which,  it 
will  be  noted,  has  a  direct  connection  to  the  feed-water  heater. 

Problems 

1.  Compute  the  increase  in  length  of  a  steam  pipe  87  feet  in  length  when 
filled  with  steam  at  10  pounds  pressure,  if  the  pipe  was  originally  at  a  tempera- 
ture of  60°. 

2.  Compute  the  increase  in  length  of  a  steam  pipe  217  feet  in  length  when 
filled  with  steam  at  125  pounds  pressure.     Original  temperature  60°. 

3.  How  much  steam  can  be  transmitted  by  a  6-inch  pipe  93  feet  long 
with  an  initial  pressure  of  5  pounds  gage  and  a  final  pressure  of  4  pounds 
gage? 

4.  How  much  steam  can  be  transmitted  by  the  same  pipe  as  in  Prob.  1, 
with  an  initial  pressure  of  105  pounds  gage  and  a  final  pressure  of  104 
pounds  gage? 

5.  What  will  be  the  drop  in  pressure  if  2,000  pounds  of  steam  per  hour  at 
an  initial  pressure  of  100  pounds  gage  are  passed  through  a  5-inch  pipe, 
87  feet  long,  containing  three  90-degree  elbows? 

6.  What  initial  pressure  will  be  required  if  110  pounds  of  steam  per 
minute  flows  through  a  4-inch  pipe  70  feet  long,  the  final  pressure  being 
51  pounds  gage?     Pipe  has  two  90-degree  elbows. 

7.  By  means  of  the  method  of  Par.  142,  compute  the  pipe  sizes  for  the 
heating  system  of  Fig.  124,  with  a  pressure  drop  through  the  system  of 
approximately  1.0  pounds. 


CHAPTER  XI 
HOT-WATER  SYSTEMS 

147.  Classification  of  Systems. — In  a  hot-water  heating  system 
the  water  flows  in  a  closed  circuit,  absorbing  heat  while  passing 
through  the  heater  and  giving  up  heat  while  in  the  radiators. 
The  force  required  for  moving  the  water  through  the  circuit  may 
be  obtained  from  either  of  two  sources.     In  the  gravity  or  "  nat- 
ural" system,  the  force  producing  circulation  is  due  to  the  differ- 
ence in  weight  of  the  hot  water  in  the  supply  pipes  and  the 
cooler  water  in  the  return  pipes;  in  forced  circulation  systems 
the  circulation  is  produced  by  means  of  a  pump. 

Gravity   systems    are   installed    in   resi- 

l^j ^ dences    and   other   buildings  of   moderate 

size.     Since  the  force  producing  circulation 

I      \E_ | in  a  gravity  system  is  small,  the  velocities 

-       *s\        1*8  are  necessarily  low  and  if  a  large  quantity 

of  water  must  be  circulated,  it  becomes 
necessary  to  use  very  large  pipes.  Con- 
sequently, in  large  buildings  or  in  groups 
of  buildings  where  the  heating  requirements 
call  for  a  large  volume  of  water,  it  is  best 
to  employ  a  pump  to  produce  a  more  rapid 
circulation,  thereby  permitting  relatively 
smaller  pipes  to  be  used. 

148.  Gravity  System.     Theory  of  Flow.1 — Fig.  126  represents 
an  elementary  gravity  system,  consisting  of  a  boiler  and  one 
radiator  with  an  expansion  tank. 

Consider  that  the  system  is  in  normal  operation  and  that  the 
heat  added  to  the  water  flowing  through  the  boiler  is  exactly 
equal  to  the  heat  leaving  the  water  in  the  radiators  and  piping. 
The  water  leaves  the  boiler  at  the  temperature  ti  and  enters  the 
radiator  at  the  temperature  t2,  some  heat  having  been  lost  during 
its  passage  through  the  pipe  BC.  In  the  radiator  the  water 
temperature  is  reduced  to  the  temperature  U,  and  during  its 

1  The  following  analysis  is  due  to  A.  H.  Barker. 

168 


Heater 


HOT-WATER  SYSTEMS  169 

passage  through  the  return  pipe  EG  it  is  further  reduced  to  the 
temperature  £4,  at  which  temperature  it  enters  the  boiler.  Let 
U  be  the  average  temperature  of  the  water  in  the  pipe  C-J  lead- 
ing to  the  expansion  tank. 

Let  H  be  the  amount  of  heat  which  is  delivered  per  hour  by  the 
radiator.  Then  if  Q  is  the  quantity  of  water  flowing  in  pounds 
per  hour 

H  =  Q(t,  -  tt)  (1) 

The  heat  lost  in  the  flow  piping  is 

ffi  =  Q(ti  -  W 
and  in  the  return  piping 

#2  =  Q(tz  -  tt) 
The  heat  added  to  the  water  at  the  boiler  is 

W  =  Q(*i  -  «4) 
Then 

H'  =  H  +  Hl  +  Hi 

The  density  of  the  water  at  the  various  points  in  the  circuit 
corresponding  respectively  to  temperatures  t\,  tz,  ts,  U  and  U 
is  DI,  Dz,  D3,  D4,  and  D5.  If  the  temperature  drop  is  uniform, 
the  average  temperature  in  each  section  may  be  taken  as  the 
mean  of  the  temperatures  at  the  ends.  The  average  density  of 

the  water  in  BC  is  then  =  Dl  *  D*  and  in  EG  =  D*  +  D*- 

—  Z 

Now  consider  the  forces  acting  on  each  side  of  the  plane  A-A 
passed  through  the  pipe  GB.  The  pressure  on  the  left  side  is 

evidently  due  to  the  column  of  water  BC  of  density  - 

2i 

plus  the  column  CJ  of  density  Z>5  and  is  equal  to 


The  pressure  on  the  right-hand  side  is  evidently 


Adding  these  pressures  algebraically,  we  obtain  for  the  result- 
it  pressure  tending  to  move  A  -A  to  the  left 


170  HEATING  AND  VENTILATION 

Let  Dp  =  Dl*  Dz  and  DR  =  ^-|"— 4 

Then  the  unit  pressure  p'  available  for  producing  circulation  is 
p'  =  h(DR  -  DF)  (1) 

It  is  evident  that  this  pressure  is  the  same  at  any  point  in 
the  circuit  BCEGB.  It  is  independent  of  the  relative  lateral 
positions  of  the  radiator  and  the  boiler  and  depends  only  on  the 
height  h  and  the  densities  DR  and  DF. 

It  is  convenient  to  express  this  pressure  as  a  "head,"  i.e.,  the 
height  of  a  column  of  water  of  the  same  density  as  that  in  the 
system  which  will  produce  the  given  pressure  at  its  base.  Let 
D  be  the  average  density  of  the  water  and  hi  the  head  equivalent 

vf 

to  the  unit  pressure  p'',  then  pf  =  hiD  and  hi  =  js  Sub- 
stituting in  equation  (1)  we  have 

(DR-DF) 

D 

hi  is  then  the  head  available  for  producing  circulation.  If  D,  DR) 
and  DF  are  expressed  in  pounds  per  cubic  foot  and  h  in  feet,  then 
hi  will  be  in  feet  of  water  column.  To  express  the  head  in  inches, 
which  is  a  more  convenient  unit,  the  right-hand  member  is  multi- 
plied by  12,  and 


The  density  D  in  equation  (2)  represents  the  average  density  of 
the  water  in  the  system.  A  close  approximation  would  be  to 
make 


D  = 
Substituting  in  (2) 


h'  is  then  the  available  circulating  head  in  inches  of  water. 

149.  Friction.  —  The  general  expression  for  the  loss  of  pressure 
due  to  friction  for  fluids  in  round  pipes  according  to  equation 
(4),  page  158,  is 

' 


HOT-WATER  SYSTEMS  171 

in  which 

P  =  loss  of  pressure  due  to  friction,  pounds  per  square  foot. 
/  =  a  constant   depending  on  the  nature  of  the   fluid  and 

of  the  pipe  wall. 

D  =  average  density  of  the  fluid,  pounds  per  cubic  foot. 
v  =  velocity,  feet  per  second. 
d  =  pipe  diameter,  feet. 
g  =  acceleration  of  gravity  =  32.2. 
L  —  length  of  pipe  in  feet. 

To  express  the  frictional  resistance  in  equation  (4)  in  terms  of 
fluid  head,  let  P  =  h"  D  in  which  P  is  in  pounds  per  square  foot 
and  D  in  pounds  per  cubic  foot,  h"  being  the  equivalent  head  in 
feet  of  the  fluid  at  density  D. 

Substituting  in  (4) 


<•> 

Let  P  =  4/,  then  h"  =  p-^-  (6) 

Now  if  v  is  expressed  in  inches  per  second,  and  d  in  inches, 
the  head  h"  will  be  expressed  in  inches  of  water,  without  any 
change  in  the  equation,  the  inch  unit  being  the  more  convenient. 

Equation  (6)  gives  the  frictional  resistance  to  flow  through 
straight  lengths  of  pipe  only.  The  resistance  due  to  elbows  and 
other  fittings  must  also  be  taken  into  account.  The  resistance  of 
such  obstructions  has  been  found  to  be  nearly  proportional  to  the 
square  of  the  velocity  of  flow,  and  may  therefore  be  expressed  in 
the  form 

av2 
2g 

in  which  a  is  a  constant  to  be  determined.     The  summation  of  all 
such  "single  resistances"  may  then  be  expressed  as 


and  the  entire  frictional  resistance  will  be 


In  order  to  impart  to  the  mass  of  water  in  the  system  the 


172  HEATING  AND  VENTILATION 

velocity  v,  a  certain  head  must  be  used  up  in  overcoming  this 

v2 
''starting  resistance"   which   is   equal  to  ~  ,  in   which   g1  ',  the 

acceleration  of  gravity,  is  expressed  in  inches  per  second  per 
second  so  that  this  last  term  will  be  expressed  in  inches  of  water 
head  as  are  the  others.  The  complete  expression  for  the  head 
required  to  start  and  to  maintain  flow  may  then  be  written 


In  which 

h"  is  in  inches  of  water  head. 

d  is  in  inches. 

L  is  in  feet. 

v  is  in  inches  per  second. 

g  is  in  feet  per  second  per  second. 

g'  is  in  inches  per  second  per  second. 

In  considering  only  the  force  required  to  maintain  a  steady 
flow,  the  last  term  does  not  enter,  however. 

150.  Condition  of  Steady  Flow.  —  When  the  circulation  in  a 
heating  system  has  become  constant,  the  head  available  for 
producing  flow  must  be  exactly  equal  to  the  frictional  resistance. 
This  condition  must  invariably  be  fulfilled.  If  the  available  head 
increases  or  decreases,  the  velocity  will  change  also  until  it 
assumes  such  a  value  that  the  frictional  resistance  will  equal  the 
available  head.  The  relation1  may  be  expressed  by  equating  the 
right-hand  members  of  equations  (3)  and  (8) 

-'+"• 


151.  Types  of  Gravity  Systems.  Two-pipe  Multiple  -circuit 
System.  —  There  are  several  different  ways  of  arranging  the 
piping  in  a  gravity  system.  The  most  common  method  for 
installations  of  moderate  size  is  the  two-pipe  multiple-circuit 
system  shown  in  Fig.  127.  The  water  leaves  the  boiler  through 
the  flow  main,  passes  through  the  radiators  and  into  the  return 
main.  A  single  pair  of  mains  may  be  installed  to  circle  the 
basement,  but  a  better  method  is  to  install  two  or  more  pairs 
which  extend  in  different  directions.  In  order  to  insure  a  suffi- 
cient flow  of  water  to  each  radiator,  it  is  best  to  provide  sepa- 

JFor  further  discussion  see  "Heating  and  Ventilation"  by  A.  H.  BARKER. 


HOT-WATER  SYSTEMS 


173 


rate  supply  and  return  risers  to  each  radiator  from  the  mains. 
Both  the  supply  and  return  mains  are  given  a  pitch  toward  the 
boiler  of  about  J-^  inch  in  10  feet,  so  that  no  air  will  accumulate  in 
the  piping  and  so  that  the  system  can  be  drained  at  the  boiler. 
Two-pipe  systems  are  often  installed  with  a  "  re  versed"  return 
main,  as  shown  in  Fig.  128.  The  flow  in  the  return  main  is  in 
the  same  direction  as  in  the  supply  main  and  is  so  arranged  that 
the  length  of  the  circuit  through  each  radiator  is  the  same.  This 
tends  to  equalize  the  resistance  to  flow  through  all  the  radiators 
and  the  system  therefore  operates  more  uniformly]throughout. 


n 


n 


ft 


FIG.  127. — Two  pipe  multiple  circuit 
system. 


FIG.   128.— Reversed  return. 


A  modification  of  the  two-pipe  system  was  formerly  used,  in 
which  separate  supply  and  return  pipes  were  provided  for  each 
radiator.  Although  such  an  arrangement  gives  good  results, 
the  complication  and  cost  of  the  piping  have  rendered  it  prac- 
tically obsolete. 

152.  Expansion  Tank. — The  change  of  volume  of  the  water 
in  a  hot-water  system  under  varying  temperatures  is  quite 
appreciable  and  an  expansion  tank  must  always  be  provided. 

The  tank  is  located  well  above  the  highest  radiator  in  the 
system  and  is  provided  with  a  vent  and  an  overflow  to  the  sewer, 
as  illustrated  in  Fig.  129.  If  located  in  an  unheated  room,  a 
connection  should  be  made  to  it  from  both  supply  and  return 
mains  to  insure  sufficient  circulation  to  prevent  freezing.  If 
possible,  the  connection  to  the  tank  should  be  taken  from  the 
supply  main  as  near  the  boiler  as  possible  so  that  the  air  which  is 
liberated  from  any  fresh  water  which  is  fed  to  the  boiler  will  rise 
to  the  expansion  tank  and  escape  rather  than  accumulate  in  the 
radiators. 


174 


HEATING  AND  VENTILATION 


The  required  capacity  of  the  expansion  tank  is  evidently  a 
function  of  the  quantity  of  water  in  the  system  and  may  be 
determined  by  computing  the  volumetric  expansion,  for  the  maxi- 
mum temperature  range,  of  the  esti-  

mated  quantity  of  water  in  the  system. 
A  rough  rule  is  to  make  the  capacity 
of  the  exp  ansion  tank  in  gallons  equal 
to  the  radiation  in  square  feet  divided 
by  40. 


Overflow  and  Vent 


FIG.  129. — Arrangement  of  expansion 
tank.1 


FIG.  130. — Two-pipe  overhead 
system.1 


153.  Two-pipe  Overhead  System. — In  Fig.  130  is  shown 
the  two-pipe  overhead  system.  The  supply  main  is  located 
in  the  attic  and  parallel  supply  and  return  risers  drop  to  the 
basement  as  shown.  This  system  is  best  adapted  to  rather 
large  buildings. 


1  From  "  Pipe-fitting  Charts"  by  W.  G.  SNOW. 


HOT-WATER  SYSTEMS 


175 


154.  One -pipe  System. — It  is  possible,  though  not  common 
practice,  to  use  a  single  pipe  for  both  flow  and  return.     A  one- 
pipe  overhead  system  is  arranged  - 
as  shown  in  Fig.    131.     The   re- 
turn  line   from   each  radiator  is 
connected  to  the  riser  at  a  point 
below  the  supply  connection.    The 
circulation   through  any  radiator 
may  be   accelerated   by  lowering 
the  point  at  which  its  return  con- 
nection reenters  the  riser,  as  at  B. 

One  disadvantage  of  this  system 
is  the  fact  that  the  cool  water  from 
the  radiators  lowers  the  average 
temperature  of  the  water  in  the 
riser  and  the  radiators  on  the 
lower  floors  are  therefore  supplied 
with  water  at  a  relatively  low 
temperature,  so  that  they  must 
have  a  larger  surface.  The  ad- 
vantages of  the  one-pipe  system 
are  its  simplicity  and  somewhat 
lower  cost. 

The  one-pipe  circuit  system  is 
shown  in  Fig.  132.  The  main 
circles  the  basement  and  separate 
connections  are  usually  taken  off 
to  each  radiator,  although  some- 
times a  first-floor  and  a  second- 
floor  radiator  are  connected  to  the 
same  risers.  The  main  should  be  of  uniform  size  throughout 
its  length.  In  large  buildings,  a  separate  main  is  sometimes 
installed  for  each  floor.  This  system  has  the  inherent  disad- 


FIG.    131.  —  One-pipe    overhead 
system. 


FIG.   132. — One-pipe  circuit  system. 


vantage  of  all  one-pipe  hot-water  systems,  that  the  temperature 
of  the  water  in  the  main  is  lowered  as  that  from  the  radiators  is 


176 


HEATING  AND  VENTILATION 


mixed  with  it  and  the  radiators  at  the  remote  end  must  there- 
fore be  of  larger  size.  Its  chief  advantage  lies  in  its  simplicity 
and  in  the  smaller  amount  of  piping  required. 

155.  Water   Temperatures. — The   water   temperatures   in   a 
hot-water  system  will  vary  according  to  the  heating  require- 
ments.    Most    ordinary    gravity    systems    are     designed     to 
operate  at  a  water  temperature,  leaving  the  heater,  of  180°  to 
190°  and  with  a  drop  in  temperature  through  the  system  of  20° 
to  30°. 

156.  Study  of  Various  Types  of  Systems. — Fig.  133  represents 
a  multiple-circuit  system  and  Fig.   134  an  overhead  system. 
The   head    available   for   producing    circulation   through    any 
radiator  is  proportional  to  the  elevation  of  the  radiator  above 
the  boiler,  and  to  the  temperature  difference  between  the  flow 
and  the  return  as  expressed  in  formula  (3),  page  170.     In  the 


^1 

m. 

a 
6 

=" 

u 

m 

"T 

L 

a' 
6' 

P 

hi                ..Lf 

il 

FIG.  133. 


FIG.  134. 


FIG.  135. 


two  types  of  systems  illustrated,  the  inlet  and  outlet  connections 
of  the  radiators  are  both  at  the  bottom  and  the  effective  height 
should  therefore  be  measured  from  the  radiator  connections  to  the 
center  of  the  boiler.  The  f  rictional  resistance  to  flow  varies  almost 
directly  as  the  length  I  of  the  circuit  from  the  boiler  through 
the  radiator  and  the  circulating  head  varies  directly  as  the 
height  h  of  the  radiator  above  the  boiler.  It  is  therefore  evident 
that  the  radiators  marked  D  in  both  figures  are  the  least  favor- 

ably situated,  since  the  ratio  K  is  the  least  for  these  radiators. 


The  size  of  the  pipes  in  the  mains  must  therefore  be  based  on 
the  circulating  head  due  to  these  radiators.  This  can  be  more 
clearly  comprehended  when  it  is  remembered  that  the  source  of 
the  circulating  force  is  the  radiator  itself.  Radiators  C  and  D, 
Fig.  133,  may  be  thought  of  as  centrifugal  pumps  of  different 
working  heads  operating  in  parallel  and  pumping  the  water 


HOT-WATER  SYSTEMS  177 

around  the  circuit.  It  is  evident  that  in  such  a  case  if  both 
pumps  are  to  deliver  water,  the  force  producing  circulation  could 
not  be  greater  than  that  developed  by  the  pump  having  the 
smaller  head,  which  corresponds  to  radiator  D. 

If  the  pipes  are  well  insulated,  the  effect  of  the  small  amount 
of  heat  lost  from  them  will  be  negligible;  if,  however,  they  are 
left  uncovered,  the  effect  on  the  circulating  head  will  be  con- 
siderable. In  the  basement  main  system,  a  loss  of  heat  in  the 
flow  mains  and  risers  tends  to  decrease  the  circulating  head,  and 
a  loss  of  heat  from  the  return  mains  and  risers  tends  to  increase 
it.  In  the  overhead  system,  a  loss  of  heat  from  the  flow  mains 
and  risers  as  well  as  from  the  return  piping  tends  to  aid  circula- 
tion, while  a  loss  from  the  main  riser  tends  to  retard  it.  This 
should  be  evident  from  a  consideration  of  the  direction  of  flow 
in  these  pipes. 

157.  Single-pipe  System.  —  In  the  single-pipe  system,  as  illus- 
trated in  Fig.  135,  the  water  reaching  the  inlet  connection  of  a 
radiator  as  at  a,  divides,  part  of  the  water  passing  through  the 
radiator  and  part  through  the  riser  from  a  to  b.     The  available 
head  for  producing  flow  through  the  radiator  depends  upon  the 
distance  a-b  and  the  difference  between  the  average  temperature 
of  the  water  in  the  radiator  and  the  water  in  the  pipe  a-b.     A 
lowering  of  the  point  at  which  the  return  connection  from  the 
radiator  enters  the  riser,  as  at  b',  Fig.  135,  will  tend  to  cause  a 
greater  portion  of  the  water  to  flow  through  the  radiator. 

The  circulation  through  the  mains  and  risers  depends  upon  the 
lowering  of  the  temperature  in  the  risers  themselves.  The  aver- 
age temperature  in  the  risers  is  not  necessarily  the  mean  of  the 
temperature  at  the  top  and  bottom,  but  depends  upon  the  pro- 
portion of  the  heat  removed  at  the  various  radiators. 

158.  Method  of  Computing  Pipe  Sizes.  —  In  order  to  make 
certain  that  the  system  will  operate  with  the  same  temperature 
drop  and  water  quantities  for  which  it  is  designed,  it  is  necessary 
that  the  available  circulating  head  be  computed  from  the  assumed 
temperatures  and  that  the  pipe  sizes  be  so  chosen  that  the  fric- 
tional  resistance  will  approximately  balance  this  circulating  head. 
This  condition  is  expressed  by  equation  (10),  page  172, 

DR-DF        Lvz  v* 


This  calculation  is,  of  course,  made  for  the  maximum  condition. 
At  other  times  the  temperature  of  the  water  leaving  the  boiler, 
12 


178 


HEATING  AND  VENTILATION 


and  consequently  the  available  circulating  head,  will  be  less 
than  under  maximum  conditions. 

In  Fig.  136  are  given  the  values  of  the  expression  24  rr~T~rr 

L>R  H-  UF 

for  various  flow  and  return  temperatures.  To  compute  the  avail- 
able circulating  head,  it  is  then  only  necessary  to  multiply  the 
values  obtained  from  the  curves  by  h,  the  height  of  the  radiator 


140 u     150 


160°      170°      180°       190 c 
.Temperature -of  Flow 

FIG.    136.1 


200°      210°     220° 


above  the  boiler.  The  height  h  should  be  taken  from  a  point 
midway  between  the  flow  and  return  connections  of  the  boiler. 
If  both  of  the  radiator  connections  are  at  the  bottom,  the  distance 
h  is  measured  to  the  connections.  If  the  inlet  connection  is  at 
the  top,  the  height  h  is  usually  measured  to  a  point  located  at 
1  By  A.  H.  BARKER. 


HOT-WATER  SYSTEMS 


179 


a  distance  above  the  bottom  connection  equal  to  one-fourth  the 
height  of  the  radiator. 

In  order  to  determine  the  pipe  friction,  it  is  necessary  to 
know  the  value  of  p.  This  has  been  determined  experimentally 
by  many  investigators,  but  their  results  differ  considerably. 

0.0595 
According  to  Weisbach,  p  =  0.01439  +  — j=-  for  water  in  iron 


100 

ter  Column  per  10  Feet  of  Pipe  ~,  g 

xbo  M  to  *  o,o>-»««5  g  g  SgS°§ 

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as  of  Head  by  Friction 
for 
Water  in  Iron  Pipes 
Temp.  160  Deg.E. 

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1  1           1  11  II  11 

S    S   3  3888  §         8    §   888  S3 

1            CO       •*         CO       00    0 

Quantity  of  Water  Flo  wing. -Pounds  per  Hour  "• 

FIG.   137. 

pipes,  v  being  the  velocity  in  inches  per  second.  The  frictional 
resistance  under  various  conditions  of  flow  is  given  by  the  chart 
in  Fig.  137  which  is  based  on  Weisbach's  value  for  p.1  Having 

1  The  results  of  later  researches,  not  fully  confirmed,  indicate  that  the 
Weisbach  coefficient  is  somewhat  high  and  also  somewhat  in  error  in  that  it 
does  not  take  into  account  any  variation  of  the  friction  with  the  pipe  diam- 
eter. However,  the  results  obtained  from  its  use  are  sure  to  be  on  the  safe 


180  HEATING  AND  VENTILATION 

given  the  weight  of  water  flowing  and  the  pipe  size,  the  resistance 
in  inches  of  water  can  readily  be  taken  from  the  chart. 

For  the  computation  of  the  resistance  of  the  fittings  or  "  single 
resistances,"  it  is  very  convenient  to  consider  that  the  resistance 
so  introduced  is  equal  to  that  of  a  certain  length  of  pipe  of  the 
same  diameter.  Approximate  determinations  of  the  value  of  a 
indicate  that  at  the  average  velocities  occurring  in  heating  work, 
the  length]  of  pipe  in  feet  equivalent  to  a  90-degree  elbow  is 
equal  to  twice  the  number  of  inches  diameter  of  the  pipe.  For 
example,  a  3-inch  elbow  is  equivalent  in  resistance  to  6  feet  of 
3-inch  pipe.  Values  for  the  various  single  resistance  are  given 
in  Table  XXXII. 

TABLE  XXXII. — VALUES  OF  SINGLE  RESISTANCES 


Equivalent  length  in  feet 
equals    diameter   in 
inches  multiplied  by 

90-degree  elbow  
90-degree  elbow  —  long  sweep 

2 
1 

45-degree   elbow 

1 

Radiator  

4* 

Boiler  

4* 

Valve. 

1  to  2 

*  Diameter  of  pipe  connections. 

The  procedure  in  calculating  the  pipe  sizes  according  to 
this  method  is  then  as  follows:  The  piping  is  completely  laid 
out  according  to  the  system  chosen,  i.e.,  whether  overhead 
or  with  basement  mains,  etc.  The  circuit  supplying  the  most 
unfavorably  situated  radiator  is  the  first  to  be  considered.  The 
pipes  in  this  circuit  are  assigned  tentative  sizes  and  the  single 
resistances  noted  and  the  equivalent  lengths  obtained  from  Table 
XXXII.  The  total  equivalent  length  of  each  section  of  the  cir- 
cuit is  then  computed  and  the  friction  drop  taken  from  the  curves 
in  Fig.  137.  The  available  circulating  head  must  next  be  corn- 
side  and  it  has  been  used  in  the  design  of  many  successful  installations.  For 
further  discussion  see: 

"The  Determination  of  Pipe  Sizes  for  Hot  Water  Heating  Systems,"  by 
F.  E.  GEISECKE,  Trans.  A.  S.  H.  &  V.  E.,  1915. 

"The  Friction  of  Water  in  Iron  Pipes  and  Elbows,"  by  F.  E.  GEISECKE, 
Trans.  A.  S.  H.  &  V.  E.,  1917.  "The  Mechanics  of  Heating  and  Ventilat- 
ing," by  KONRAD  MEIER.  "Heating  and  Ventilating"  by  A.  H.  BARKER. 


HOT-WATER  SYSTEMS  181 

puted.     From  the  curves  in  Fig.  136,  the  value  of  24  n--  r— p.- 

JDR-\-  Up 

is  found  for  the  flow  and  return  temperatures  which  have  been 
assumed.  This  value,  multiplied  by  the  height  in  feet  of  the 
radiator  under  consideration,  above  the  boiler,  gives  the  circulat- 
ing head  in  inches  of  water.  If  the  friction  head  does  not  agree 
within  about  5  per  cent,  with  the  circulating  head,  as  it  probably 
will  not  in  the  first  calculation,  the  size  of  some  of  the  pipes  in 
the  circuit  must  be  changed  and  the  total  friction  drop  again 
computed.  By  successive  refinements  the  two  quantities  can  be 
made  nearly  equal.  This  circuit  having  been  established,  the 
circuits  to  the  other  radiators  are  worked  out  in  a  similar  manner, 
the  parts  in  common  with  the  circuit  first  computed  being  left 
as  first  set  down.  In  the  case  of  a  single-pipe  system,  the  cir- 
culation to  the  most  unfavorably  situated  riser  is  first  computed, 
with  the  circulating  head  taken  as  that  due  to  the  riser. 

159.  Necessity  of  Accurately  Choosing  the  Pipe  Sizes. — Let 
us  examine  the  effect  of  an  improper  selection  of  pipe  sizes. 
There  are  three  possible  ways  in  which  errors  can  be  made. 

I.  By  making  all  the  parts  of  the  system  too  small  but  of  the 
proper  relative  size. 

II.  By  making  all  of  the  pipes  too  large. 

III.  By  making  the  resistance  of  some  circuits  much  greater 
than  that  in  the  others. 

If  the  pipe  sizes  are  all  too  small,  the  primary  effect  will  be  to 
decrease  the  quantity  of  water  passed  through  the  entire  system 
in  unit  time.  If  the  temperature  of  the  water  leaving  the  boiler 
is  kept  constant,  the  effect  of  the  decrease  in  the  quantity  will  be 
to  increase  the  temperature  drop  in  the  radiators.  This  will 
increase  the  available  circulating  head  which  will  in  turn  increase 
the  velocity  of  flow.  Unless  the  error  is  extreme,  the  system  will 
therefore  approach  the  performance  set  for  it. 

If  the  pipes  are  too  large  throughout,  the  primary  effect  will  be 
to  increase  the  flow  of  water  through  the  system.  This  will  cause 
a  decrease  in  the  temperature  drop  through  the  radiators,  a  reduc- 
tion in  the  circulating  head,  and  a  consequent  reduction  of  the 
flow  to  some  value  approaching  the  proper  one.  The  same  action 
takes  place  in  the  case  of  the  individual  circuits  or  radiators. 
If  the  pipes  are  too  small,  the  reduction  in  flow  causes  an  increase 
in  the  temperature  drop  and  the  net  result  is  usually  but  a  slight 
decrease  in  the  heat  delivered  to  the  room. 


182 


HEATING  AND  VENTILATION 


It  is  thus  apparent  that  gravity  hot-water  systems  are  to  some 
extent  self -regulating.  It  is  due  to  this  property  that  the  ordinary 
hot-water  systems,  installed  without  exact  design,  operate  with 
satisfaction.  Indeed,  for  the  usual  small  system  it  is  not  practi- 
cable to  make  exact  calculations  of  the  pipe  sizes,  experience 
having  evolved  empirical  rules  which  give  pipe  sizes  which  are 
on  the  safe  side  and  produce  entirely  acceptable  results.  While 
the  heat  delivered  to  the  rooms  may  vary  by  several  per  cent, 
from  the  theoretical  requirements,  the  error  is  well  within  that 
due  to  inaccuracies  in  computing  the  heat  losses  from  the  room. 

In  large  installations,  the  exact  method  has  some  distinct 
advantages.  The  liberality  with  which  the  pipe  sizes  of  a  small 
system  are  selected  cannot  be  practiced  on  a  large  system  without 
a  considerable  increase  in  the  cost  of  the  installation,  while  any 
pipes  which  may  be  chosen  too  small  can  be  replaced  only  at  great 
expense.  Throttling  valves,  while  they  should  be  placed  on  the 
branch  circuits  as  a  precaution,  are  difficult  to  adjust  and  are 
easily  tampered  with.  A  calculation  of  the  pipe  sizes  in  the 
manner  outlined  is  therefore  desirable  for  large  or  important 
installations. 

160.  Approximate  Rules  for  Pipe  Sizes. — Table  XXXIII  gives 
the  capacity  of  mains  of  various  pipe  sizes  for  different  kinds  of 
systems. 

TABLE  XXXIII.— SIZE  OF  MAINS 
Assumed  Length  100  Feet,  Temperature  Drop  in  Radiators  20° 


Pipe  diam. 

Capacity,  square  feet  of  direct  radiation 

Two-pipe  upfeed 

One-pipe   upfeed 

Overhead 

m 

75 

45 

130 

m 

110 

65 

190 

2 

200 

121 

340 

V/2 

310 

190 

530 

3 

540 

330 

920 

3^ 

780 

470 

1,330 

4 

1,100 

650 

1,800 

5 

1,900 

1,100 

3,200 

6 

3,000 

1,800 

5,000 

7 

4,300 

2,700 

7,200 

8 

5,900 

3,500 

9,900 

Table  XXXIV  gives  the  capacity  of  risers  in  square  feet  of 
radiation 


HOT-WATER  SYSTEMS 


183 


TABLE  XXXIV.— SIZE  OF  RISERS 
Assumed  Temperature  Drop  in  Radiators,  20C 


Pipe 

size 

Upfeed 

Downfeed  risers,  not 
exceeding  four  floors 

First 
floor 

Second 
floor 

Third 
floor 

Fourth 
floor 

1 

33 

46 

57 

64 

48 

1/4 

71 

104 

124 

142 

112 

l/^ 

100 

140 

175 

200 

160 

2 

187 

262 

325 

375 

300 

23^ 

292 

410 

492 

580 

471 

3 

500 

755 

875 

1,000 

810 

The  following   schedule   of  tappings   is  used  for  hot-water 
radiators : 

TABLE  XXXV. -RADIATOR  TAPPINGS 

Size  of  radiator  Supply  and  return  tapping 

Up  to  40  square  feet 1      inch 

40  to  72  square  feet \y±  inches 

Over  72  square  feet 1^  inches 

161.  Piping. — Many    of  the    principles  governing  the  design 
of  steam  piping  apply  to  hot-water  work.     Expansion  must  be 
provided  for  with  care,  although  it  is  less  in  amount.     Connec- 
tions and  fittings  must  be  installed  so  as  to  interpose  as  little 
resistance  to  flow  as  possible.     The  venting  of  the  air  from  the 
system  is  important.     In  addition  to  a  vent  at  the  expansion 
tank,  a  small  pet-cock  should  be  provided  on  each  radiator  and 
at  any  other  points  at  which  air  may  accumulate.     Mains  should 
be  given  a  pitch  of  at  least  %  inch  in  10  feet  toward  the  boiler 
and  provision  should  be  made  for  draining  the  water  from  the 
entire  system  as  is  necessary  when  the  plant  is  shut  down  in  cold 
weather. 

162.  Closed  Systems. — In  the  open-tank  systems  which  have 
been  described,  the  water  temperature  is  limited  to  212°  because 
the  pressure  at  the  top  of  the  system  is  at  atmosphere;  but  if  the 
pressure  of  the  water  at  the  top  of  the  system  is  raised  above 
atmosphere,  its  boiling  point  and   consequently  the  allowable 
temperature  is  raised,  increasing  the  heat  output  of  the  system. 
For  maintaining  the  increased  pressure  on  the  system,  some 
device  such  as  a  mercury  seal  is  inserted  in  the  pipe  leading  to  the 
expansion  tank.     One  form  of  these  so-called  "generators"  is 


184 


HEATING  AND  VENTILATION 


shown  in  Fig.  138.  The  water  from  the  system,  as  its  tempera- 
ture rises,  exerts  an  increasing  pressure  on  the  surface  of  the 
mercury  in  the  chamber  B,  forcing  mercury  up  the  tube  A  until 
it  bubbles  out  of  the  top  of  the  tube.  A  pressure  equivalent  to 
the  height  of  the  mercury  column  thus  formed  may  be  built  up 
at  the  top  of  the  system  and  the  water  may  be  heated  nearly  to 
the  corresponding  boiling  point.  As  the  water  in  the  system 
cools  and  decreases  in  volume,  the  mercury  falls  down  the  tube 
and  more  water  enters  the  system  from  the  expansion  tank. 


To  Expansion  Tank 


FIG.  138. — Mercury  seal  "generator." 

Generators  are  especially  useful  for  increasing  the  output  of  a 
heating  system  which  has  been  inadequately  designed  or  which 
has  become  inadequate. 

163.  Forced  Circulation. — When  hot-water  heating  is  used  in 
large  buildings  or  groups  of  buildings,  the  circulating  power  is 
obtained  from  a  pump  and  smaller  pipes  are  used,  the  water  flowing 
at  much  higher  velocities  than  in  a  gravity  system.  In  systems 
employing  forced  circulation,  the  water  usually  passes  through 
the  pump,  then  to  the  heater,  and  to  the  radiators.  The  piping 
is  arranged  in  the  same  general  manner  as  in  the  gravity  systems. 
The  action  is  somewhat  different  from  that  in  the  gravity  systems 


HOT-WATER  SYSTEMS  185 

in  that  the  force  producing  circulation  is  from  the  pump  and  not 
from  the  cooling  action  of  the  radiators ,  for  although  the  tempera- 
ture difference  in  the  system  has  some  effect,  it  is  so  far  over- 
balanced by  the  force  exerted  by  the  pump  as  to  be  negligible. 
The  flow  through  the  various  parts  of  the  system  is  therefore 
governed  to  a  greater  extent  by  the  frictional  resistance,  as  the 
system  does  not  possess  the  self-regulating  qualities  of  the 
gravity  system. 

164.  Pumpage,  Friction,  and  Temperature  Drop. — The  quan- 
tity of  heat  delivered  per  hour  may  be  expressed  by  the  equation 

H  =  Q  (tl-  <2)  (1) 

in  which         H  =  quantity  of  heat  delivered  per  hour. 

Q  =  weight  of  water  pumped  per  hour. 
ti  —  tz  =  drop  in  temperature  of  water. 

It  is  evident  that  the  quantity  of  water  and  the  temperature 
drop  may  vary,  the  requirement  being  that  their  product  remain 
constant.  As  the  temperature  drop  is  increased,  however,  the 
average  temperature  of  the  radiators  is  lowered  and  somewhat 
more  surface  must  be  installed.  It  is  common  practice  to  allow 
a  temperature  drop  under  maximum  conditions  of  about  20°. 

Before  a  circulating  pump  can  be  intelligently  selected,  it 
is  necessary  to  choose  the  differential  pressure  at  which  the  system 
is  to  be  operated.  If  a  large  pressure  drop  is  allowed,  the  pipes 
can  be  made  relatively  small,  but  the  power  required  for  pumping 
the  water  will  be  greater.  Although  it  is  true  that  the  energy 
used  up  in  friction  is  converted  into  heat  and  is  therefore  utilized, 
the  energy  thus  recovered  is  only  a  portion  of  the  energy  input 
to  the  pumping  unit.  The  cost  of  the  power  must  therefore  be 
taken  into  consideration.  If  the  pump  is  steam-driven  and  the 
exhaust  used  for  heating  the  water,  the  cost  of  power  will  be 
lower  than  if  current  is  purchased  for  a  motor-driven  pump.  In 
each  case  a  study  should  be  made,  balancing  the  annual  invest- 
ment charges  of  the  piping  system  against  the  cost  of  power  to 
determine  the  most  economical  combination.  The  pressure 
drop  usually  allowed  is  from  10  to  30  pounds.  The  velocity  of 
flow  in  the  pipes  is  limited  to  about  40  inches  per  second  in  build- 
ings where  the  noise  produced  by  a  higher  velocity  would  be 
objectionable.  In  industrial  buildings,  no  such  limit  is  imposed. 

165.  Calculation  of  Pipe  Sizes. — The  calculation  of  the  pipe 
sizes  in  a  forced  circulation  system  is  much  more  important 


186 


HEATING  AND  VENTILATION 


than  in  a  gravity  system,  because  the  former  does  not  possess 
the  self -regulating  property  of  the  gravity  system.  If  any 
one  circuit  is  unfavorably  designed,  there  will  be  a  tendency 
for  it  to  be  short-circuited.  Furthermore,  the  resistance  of  the 
entire  system  must  be  made  approximately  equal  to  the  rated 
head  of  the  pump.  The  procedure  in  designing  a  forced  cir- 
culation system  is  as  follows.  The  heat  loss  from  the  building 
having  been  computed,  the  temperature  drop  in  the  radiators  is 
chosen  and  the  amount  of  water  to  be  supplied  per  hour  is  com- 


3  91,200  Lbs.per  Hr.    4              70,050               5             00,840              r 

4i 

! 

42 

I 

13 
ll 

! 

45 
15 
47 
43 

49 
| 
5U 

I 

51 

7 
8 
9 

;      „ 

' 

12 
13 
14 
15 
16 
17 

-D-i 
-O- 
JT3- 

18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 

-O-i 

^a- 

4^- 

-n- 
-o- 
-n- 
-n- 

-O- 
-Q- 

-o- 

H=l- 

~l==h 

-p- 
-n- 
-n- 
-i=h 
_n- 

30 
31 
32 
33 
34 
35 

| 

th 

1,607 

-n- 
-n- 
-n- 
-o- 

-Tl- 

JT3- 

-n- 

-0- 
_rn- 

-TT 

36 
37 

'  38 
39 
40 

4=1- 
-t=h 
4=V 
^=h 
-1=1- 

-n- 

-JZJ- 

-O- 

-TV 

4=^- 
-D- 

4=}- 

-n- 

9  91,300  54  76,150  53         60.840 


FIG.  139. 

puted  from  formula  (1),  Par.  164.  From  a  consideration  of  the 
various  factors  mentioned  in  the  preceding  paragraph,  the  differ- 
ential head  is  chosen  and  a  pump  is  selected  which  will  operate 
most  efficiently  under  the  given  conditions.  The  piping  must 
then  be  designed  so  that  this  differential  pressure  is  used  up  in 
friction. 

The  general  scheme  followed  in  choosing  the  pipe  sizes  is 
similar  to  that  used  for  a  gravity  system,  the  available  circulating 
head,  which  in  this  case  is  produced  by  the  pump,  being  balanced 
by  the  pipe  friction. 


HOT-WATER  SYSTEMS 


187 


The  method  can  best  be  explained  by  working  out  a  specific 
installation.  In  Fig.  139  is  shown  diagrammatically  one  part 
of  an  overhead  two-pipe  system.  The  weight  of  water  flowing 
per  hour  is  indicated  for  the  circuit  which  supplies  the  radiator 
marked  30-41,  the  assumption  being  made  that  these  water 
quantities  have  been  computed  in  the  manner  previously 
explained.  The  circuit  through  this  radiator  is  the  longest  and 
should  therefore  be  computed  first  and  the  other  parallel  circuits 
designed  to  give  the  same  resistance.  In  column  4,  Table 
XXXVI,  the  actual  length  of  each  section  of  the  circuit  is  given. 
The  system  will  be  designed  on  a  basis  of  a  pressure  differential 
of  10  pounds.  The  length  of  the  circuit  is  481  feet.  The  average 

TABLE    XXXVI. — CALCULATION    OF    PIPE    SIZES — FORCED    CIRCULATION 

SYSTEM 


s 

Q 

IH 

43 

OQ 

O  o 

03 

^ 

le- 

|-S 

.9 

i 

a 

7*3, 

c 

g 

8 

1 

II 

a 

a 

IH 

0 

a 

£ 

1 

13 

ft's 

§ 

Number  of 

"o  a 

111 

O?s3  a 

Proposed  di 

1e 

•g 

la 

J* 

Single  resist 

p 

Resistance 
feet  length 

I 

3 
£ 

a 
'a 

|a 

Single  resisi 

o1 
if 

Resistance 
feet  length 

1 

3 

o 
H 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

1-2 

106,470 

4 

21 

1  X  8 

29 

4.0 

11.6 

2-3 

106,470 

4 

158 

3X8 

182 

4.0 

72.8 

3-4 

91,260 

3 

22 

22 

9.4 

20.7 

4-5 

76,050 

3 

22 

22 

6.8 

15.0 

5-6 

60,840 

3 

22 

22 

4.6 

10.1 

2H 

22 

9.0 

19.8 

6-30 

15,210 

2 

10 

1  X  4 

14 

2.4 

3.4 

IH 

1  X  3 

13 

7.5 

9.8 

30-41 

1,667 

1 

8 

2X2 

12 

0.9 

1.1 

41-42 

1,667 

1 

12 

12 

0.9 

1.1 

42-43 

3,000 

1 

12 

12 

2.8 

3.4 

43-44 

4,333 

1 

12 

12 

5.2 

6.2 

44-45 

5,667 

12 

12 

2.7 

3.2 

45-46 

7,000 

1  }>4 

12 

12 

3.9 

4.7 

46-47 

8,333 

1  /"i 

12 

12 

5.3 

6.4 

47-48 

9,667 

I/-  2 

12 

12 

3.3 

4.0 

48-49 

11,000 

1W 

12 

12 

4.1 

4.9 

49-50 

12,333 

l1^ 

12 

12 

4.9 

5.9 

50-51 

13,667 

IJ  , 

12 

12 

5.9 

7.1 

51-52 

15,210 

2' 

3 

1  X  4 

7 

2.4 

1.7 

52-53 

60,840 

3 

22 

22 

4.6 

10.1 

214 

22 

9.0 

19.8 

53-54 

76,150 

3 

22 

22 

6.8 

15.0 

54-29 

91,360 

3 

22 

. 

22 

9.4 

20.7 

29-55 

106,470 

4 

29 

3X8 

53 

4.0 

20.2 

Total  

249.3 

275.  1 

Pounds 

8.8 

9.7 

188  HEATING  AND  VENTILATION 

friction  loss  per  10  feet  of  pipe  in  inches  of  water  column  at  a 


1  0 
temperature  of  160°  will  be  40  i  v~fii~n  =   ^  mcnes  °f  water. 

With  the  given  quantities  of  water  flowing,  and  using  a  friction 
loss  of  approximately  5.9  inches  per  10  feet,  the  pipe  sizes  can 
be  chosen  from  the  chart  in  Fig.  137,  page  179.  They  are  set 
down  in  column  3.  The  length  equivalent  to  the  single  resis- 
tances is  computed  and  the  total  equivalent  lengths  set  down  in 
column  6.  From  the  friction  chart  the  resistance  per  10  feet 
for  each  section  is  found.  These  are  multiplied  by  the  equiva- 
lent lengths  and  the  results  set  down  in  column  8.  The  sum 
of  all  of  them  is  found  to  be  249.3  inches  of  water  which  is  equal 
to  8  .  8  pounds  as  against  the  10  pounds  originally  specified.  The 
sections  5-6,  6-30,  and  52-53  may  be  decreased  one  pipe  size 
to  increase  the  resistance,  as  given  in  columns  9  to  13.  The 
total  resistance  will  then  be  275.1  inches  or  9.7  pounds  which 
is  sufficiently  close  to  the  desired  resistance.  The  circuit  2-3-5- 
53-29-55  and  all  of  the  remaining  circuits  must  then  be  worked 
out  in  a  similar  manner  to  give  an  equal  resistance,  the  parts 
which  have  already  been  computed  being  left  as  they  stand. 
It  is  desirable  to  install  a  "lock  and  shield"  valve  on  each  riser 
and  at  each  radiator  in  order  that  the  distribution  can  be 
adjusted  after  the  system  is  completed. 

166.  Pumps.  —  Either  the  centrifugal  or  the  reciprocating  pump 
may  be  used  to  produce  the  circulation;  but  the  centrifugal  type 
is  by  far  the  more  suitable.  It  possesses  the  advantages  of  pro- 
ducing a  uniform  flow  of  water,  does  not  transmit  jars  or  vibration 
to  the  piping,  requires  little  attendance,  and  is  economical  in 
operation.  Centrifugal  pumps  may  be  driven  by  either  a  steam 
turbine  or  a  motor,  the  former  drive  being  used  when  high-pres- 
sure steam  is  available. 


CHAPTER  XII 
TEMPERATURE  CONTROL 

167.  Manual  Control. — In  every  heating  system  the  radiators, 
boiler,  and  other  component  parts  are  selected  on  the  basis  of  the 
maximum  requirements,  i.e.,  for  the  lowest  outside  temperature 
which  is  to  be  expected.  Consequently  the  capacity  of  the  sys- 
tem is  much  greater  than  is  required  in  average  winter  weather. 
In  many  localities,  for  example,  where  heating  plants  are 
designed  for  a  minimum  outside  temperature  of  0°,  the  average 
temperature  for  the  heating  season  is  from  35°  to  40°.  In 
order  to  prevent  excessive  room  temperatures  the  heat  output 
of  the  system  must  be  regulated,  either  manually  or  automatically, 
to  correspond  approximately  with  the  heat  losses  from  the 
building. 

Temperature  control  is  accomplished  in  different  ways  accord- 
ing to  the  kind  of  heating  system  and  the  nature  of  the  building. 
In  many  cases  manual  control  of  the  radiators  or  of  the  furnace 
drafts  is  all  that  is  necessary;  in  other  cases,  automatic  tem- 
perature control,  applied  to  the  individual  radiators,  is  very 
desirable.  In  hot-air  furnace  installations  and  in  small  steam  and 
hot-water  systems  the  universal  method  is  to  regulate  the  heat 
output  of  the  boiler  or  furnace  by  adjusting  the  drafts.  When 
the  building  is  large,  however,  it  is  often  impossible  to  regulate 
accurately  the  temperature  throughout  the  building  by  this 
means  and  control  of  the  radiators  must  be  resorted  to.  In 
vapor  systems  equipped  with  graduated  inlet  valves  accurate 
control  is  possible  if  sufficient  attention  is  given  by  the  occupants 
of  the  room  to  the  adjustment  of  the  valves. 

In  single-pipe  steam  systems  the  supply  of  steam  to  each 
radiator  cannot  be  controlled.  It  is  therefore  sometimes  desir- 
able to  provide  at  least  two  radiators  in  each  room  so  that  one  or 
both  can  be  used  as  required. 

In  a  vacuum  steam  system  the  heat  output  can  be  varied  within 
certain  limits  by  varying  the  steam  pressure.  For  example,  if  the 
steam  pressure  can  be  varied  from  10  inches  of  vacuum  to  10 
pounds  pressure,  the  temperature  of  the  radiating  surfaces  will 

189 


190 


HEATING  AND  VENTILATION 


FIG.  140. — Bellows 
thermostat. 


change  from  193.2°  to  240.1°,  which,  if  the  room  temperature 
is  70°,  would  give  a  range  of  heat  output  of  about  38  per  cent. 
This  is  about  the  maximum  range  which  could  be  secured  by  this 
means. 

168.  Automatic  Control  Applied  to  Boiler  or  Furnace. — Tem- 
perature control  by  adjusting  the  drafts  of  the  boiler  or  furnace 
can  be  accomplished  automatically  by  means 
of  any  one  of  several  designs  of  thermostats. 
The  simplest  of  these  consists  of  a  bellows 
containing  a  volatile  liquid  which  causes  an 
expansion  and  contraction  of  the  bellows 
with  changes  of  temperature.  The  bellows 
is  installed  at  the  point  from  which  the  tem- 
perature is  to  be  controlled  and  its  move- 
ment is  transmitted  by  means  of  a  cable  to 
the  dampers  on  the  boiler  or  furnace  in  such  away  that  a  lowering 
of  the  room  temperature  causes  an  increase  in  the  air  supply 
to  the  fuel  bed  and  a  resulting  increase  in  the  heat  output.  This 
form  of  thermostat  is  shown  in  Fig.  140. 

In  another  form  of  thermostat  the  dampers  are  operated  by  a 
motor  located  in  the  basement 
and  started  electrically  from  a 
controller  placed  in  the  room 
above.  Fig.  141  illustrates  the 
controller  of  such  a  thermostat. 
The  member  A  consists  of  two 
strips  of  metals,  having  different 
coefficients  of  expansion,  brazed 
together.  This  member  is  fixed 
at  point  B  and  the  end  C  is 
deflected  to  the  right  or  left  by 
the  unequal  expansion  of  the 
metals  with  changes  of  tempera- 
ture. The  controller  is  con- 
nected electrically  with  the 
motor  in  such  a  way  that,  as  the  temperature  drops  and  the 
strip  C  makes  a  contact  with  D,  a  current  of  low  voltage  is 
transmitted  through  the  circuit,  and,  by  means  of  a  relay,  starts 
the  motor,  which  opens  the  drafts  on  the  boiler.  Similarly, 
a  slight  increase  of  temperature  above  the  established  point 
causes  a  contact  to  be  made  between  C  and  E  and  the  motor 


FIG.    141. — Controller   for    damper 
thermostat. 


TEMPERATURE  CONTROL 


191 


is  started,  closing  the  drafts.  The  temperature  for  which  the 
controller  is  set  can  be  changed  by  moving  the  knob  F  which  shifts 
the  position  of  D  and  E.  The  controller  can  be  obtained  with  a 
clock  mechanism  which  will  cause  the  drafts  to  close  at  night 
and  to  open  in  the  early  morning  at  some  predetermined  time. 
The  motor  may  be  a  clock  mechanism,  in  which  the  energy  is 
obtained  from  a  spring  which  is  wound  periodically  by  hand. 
The  electric  motor  is  more  desirable,  however,  as  it  requires  no 
winding.  The  method  of  connecting  the  motor  to  the  dampers  is 
shown  in  Fig.  142. 


Wire 


FIG.  142. — Method  of  connecting  thermostat. 

In  installing  this  form  of  thermostat  the  location  of  the  con- 
troller is  of  prime  importance.  As  the  heat  supply  for  the  entire 
building  is  to  be  controlled  from  one  point,  it  is  essential  that  the 
controller  be  installed  in  some  central  location  where  the  tem- 
perature is  approximately  an  average  of  that  in  the  entire 
building.  It  is  the  difficulty  of  controlling  the  temperature 
satisfactorily  from  a  single  point  that  limits  the  use  of  such 
thermostats  to  residences  and  small  buildings. 

These  devices  do  not  maintain  an  absolutely  constant  tempera- 
ture. There  is  usually  a  noticeable  rise  and  fall  in  the  tempera- 
ture because  of  the  sluggishness  with  which  the  furnace  or  boiler 


192 


HEATING  AND  VENTILATION 


responds  to  the  opening  and  closing  of  the  dampers.     In  the 

average  case  a  variation  in  the  tem- 
perature at  the  thermostat  of  from 
four  to  six  degrees  must  be  expected. 
169.  Automatic  Control  Applied  to 
Individual  Radiators. — In  large  build- 
ings, in  order  to  regulate  the  tem- 
perature automatically,  the  radiators 
in  the  various  rooms  must  be  operated 
as  separate  units,  by  means  of  a  con- 
troller located  in  each  room.  The 
power  for  operating  the  radiator 
valves  is  obtained  from  compressed 
air,  supplied  from  a  central  source, 
and  the  air  supply  to  the  individual 
FIG.  143. Radiator  valve  radiator  valves  is  regulated  by  a  small 

for  compressed  air  system  of    valve  operated  by  the  expansion  ele- 
ment in  the  controller.     The  system 


temperature  regulation. 


may  be  designed  so  that  the  radiator  valves  are  either  fully  open 
or  fully  closed,  or  the  amount  of  opening  may  be  graduated 


FIG.  144. 


FIG.  145a. 
Compressed  air  thermostat. 


FIG.  145&. 


according  to  the  room  temperature.     The  former  arrangement  is 
necessary  on  single-pipe  radiators  and  is  known  as  the  " positive" 


TEMPERATURE  CONTROL  193 

type,  while  the  latter  or  " graduated"  type  is  applicable  to  steam 
radiators  having  a  separate  return  connection,  and  to  hot-water 
radiators. 

The  type  of  radiator  valve  used  is  shown  in  Fig.  143.  The 
valve  is  closed  when  air  under  sufficient  pressure  is  admitted 
to  the  space  surrounding  the  corrugated  metal  bellows.  When 
the  air  pressure  is  released  the  spring  forces  the  valve  open.  If  a 
pressure  less  than  that  required  to  close  the  valve  exists  around 
the  bellows  the  valve  will  take  an  intermediate  position  depending 
on  the  amount  of  that  pressure.  In  the  graduated  system 
the  intermediate  positions  of  the  radiator  valve  are  obtained  by 
creating  this  partial  pressure. 

A  common  design  of  compressed-air  thermostat1  of  the  positive 
type  is  shown  in  Fig.  144. 


1  The  operation  of  the  thermostat  is  as  follows: 

Compressed  air  is  supplied  to  the  thermostat  at  15  pounds  per  square  inch 
through  the  tube  B.  Another  tube  A  leads  to  the  diaphragm  valve  on 
the  radiator.  Passage  way  C  around  the  valve  stem  is  an  exhaust  passage 
to  the  free  air.  Compressed  air  from  B  is  admitted  to  and  exhausted  from 
A  by  the  threeway  valve  M,  the  action  of  which  will  be  explained  later.  A 
very  small  portion  of  the  compressed  air  from  the  supply  pipe  B  passes 
through  D  and  a  small  orifice  E  to  chamber  G  and  exhaust  port  F  allows 
the  air  to  escape  from  chamber  G  faster  than  it  can  enter  through  E  when 
the  thermostat  is  in  the  position  shown  in  Fig.  145o.  Fig.  145a  shows  the 
position  of  the  various  parts  of  the  thermostat  when  the  room  has  reached 
the  proper  temperature  and  the  thermostat  has  closed  off  the  steam  valve 
on  the  radiator.  The  thermostatic  bi-metal  bar  H,  which  is  composed 
of  two  metals  having  different  coefficients  of  expansion  welded  together  in 
the  form  of  a  bar,  will  be  in  the  position  which  allows  the  air  entering  cham- 
ber G  to  escape  through  F  faster  than  it  enters  at  E,  with  the  result  that 
the  diaphragm  (7)  will  be  in  a  collapsed  position.  Connected  to  this  dia- 
phragm (7)  is  a  lever  J  fulcrumed  at  its  lower  end  and  provided  at  the 
upper  end  with  a  chamber  containing  a  spring  K.  Spring  K  is  a  coil  spring 
which. wraps  itself  around  a  ball  L  attached  to  the  stem  of  valve  M.  In  the 
position  shown  in  Fig.  145a  the  spring  K  acting  on  the  ball  L  tends  to  hold 
the  valve  M  tight  against  the  exhaust  port  C  thereby  allowing  the  com- 
pressed air  to  pass  from  the  pipe  B  to  the  pipe  A  and  thence  to  the  diaphragm 
operated  valve  on  the  radiator  causing  same  to  close.  The  thermostatic 
bi-metal  bar  H  is  so  constructed  that  as  the  temperature  in  the  room  falls 
this  bar  will  move  to  the  left  causing  the  passage  F  to  close  as  shown  in  Fig. 
1456.  Now  as  the  air  can  no  longer  escape  from  F  it  will  pass  into  chamber  G 
through  the  passage  E  and  accumulate  behind  the  diaphragm  (7)  causing 
(7)  to  bulge  outward,  forcing  lever  J  to  the  right.  Lever  J  causes  the  spring 
K  to  ride  over  the  top  of  the  ball  L.  The  moment  K  passes  the  widest 
diameter  of  the  ball  L  it  will  contract  on  the  ball,  forcing  the  ball  L  suddenly 

13 


194  HEATING  AND  VENTILATION 

170.  Compressors. — The  air  supply  is  obtained  from  a  small 
compressor,  usually  motor-driven,  located  in  the  basement.  A 
storage  tank  is  required  and  a  constant  pressure  is  maintained 
in  the  tank  by  means  of  a  governor  which  automatically  starts 
and  stops  the  compressor,  as  required.  The  pressure  carried 
on  the  tank  is  usually  about  25  pounds  per  square  inch. 

The  mixing  dampers  and  the  heating  coils  of  a  fan  system  can 
be  readily  controlled  by  thermostats,  through  the  use  of  a  dia- 
phragm motor  as  shown  in  Fig.  146.  The  control  of  humidity 
is  also  possible  by  the  use  of  similar  devices.  These  applications 
will  be  considered  more  fully  under  "Fan  Systems." 


FIG.   146. — Diaphragm  motor. 

171.  Advantages  of  Automatic  Control. — The  advisability  of 
installing  a  system  of  thermostatic  control  depends  largely  upon 
the  type  of  building  under  consideration.  The  compressed  air 
type  of  thermostat  is  a  rather  delicate  apparatus  and  should 
not  be  installed  in  any  building  where  it  will  not  be  given  the 
proper  attention.  The  accuracy  of  control  which  is  obtained 
varies  in  different  cases.  Usually  a  large  room  with  several 
thermostats  and  radiators  will  be  kept  at  a  more  constant 
temperature  than  a  very  small  room.  The  principal  advan- 
tages of  thermostatic  control  are  the  convenience  and  the 
increased  comfort  which  it  affords  the  occupants.  Without  any 

to  the  left  thereby  opening  the  exhaust  port  C  and  closing  off  the  supply 
of  compressed  air  from  B.  The  compressed  air  in  the  pipe  A  leading  to 
the  diaphragm  operated  radiator  valve  will  then  be  exhausted  through  the 
passage  C  causing  the  radiator  valve  to  open  and  admit  more  heat  to  the 
room.  The  spring  K  is  a  continuous  coil  spring  in  the  form  of  a  ring 
embracing  the  ball  L.  The  action  of  the  spring  on  the  ball  is  such  that  the 
valve  can  never  be  centered  between  the  inlet  and  exhaust  ports,  but  will 
always  be  on  one  or  the  other  port  and  when  the  valve  changes  it  does  so 
instantaneously  giving  thereby  a  quick  action  to  the  diaphragm  operated 
radiator  valve.  As  the  thermostatic  bar  H  has  no  work  to  perform  beyond 
that  of  closing  the  very  small  passage  F  it  is  extremely  sensitive  to  rapid 
changes  in  temperature.  The  operation  of  a  graduated  thermostat  is 
somewhat  similar  except  that  the  mechanism  takes  up  intermediate  posi- 
tions depending  upon  the  amount  of  deflection  of  the  member  H,  and  the 
pressure  in  the  pipe  A  is  varied  accordingly. 


TEMPERATURE  CONTROL  195 

manipulation  of  the  radiator  valves,  the  temperature  of  the  rooms 
is  maintained  at  the  most  comfortable  point,  regardless  of  the 
outside  temperature.  In  many  cases  a  considerable  saving  in 
fuel  can  be  effected  by  the  use  of  automatic  control,  due  to  the 
fact  that  with  manual  control  there  is  always  a  tendency  for 
the  rooms  to  become  overheated  through  lack  of  attention  to  the 
radiator  valves.  This  may  be  true  even  when  graduated  valves 
or  other  means  of  facilitating  hand  control  are  provided.  The 
actual  amount  of  the  saving  in  fuel  is  problematical,  being  given 
by  many  as  from  10  to  30  per  cent.  In  the  average  case  it  is 
probable  that  the  lower  figure  is  the  more  nearly  correct. 

The  objections  to  the  compressed-air  systems  of  thermostat ic 
control  are  the  rather  high  initial  cost  of  the  apparatus  and  the 
cost  of  maintaining  and  of  keeping  in  adjustment  the  various 
parts  of  the  system.  Thermostatic  control  is  especially  desirable 
for  hotels,  schools,  office  buildings,  and  other  buildings  of  a  public 
character.  For  fan  systems,  automatic  control  of  the  dampers 
and  coils  is  very  much  to  be  desired,  and  in  most  cases  is  abso- 
lutely necessary  if  satisfactory  results  are  to  be  obtained. 


CHAPTER  XIII 
AIR  AND  ITS  PROPERTIES 

172.  Composition  of  Air. — The  atmosphere  of  the  earth  is  a 
mixture  of  several  gases  and  vapors,  the  proportions  of  which 
vary  somewhat  in  different  localities  and  under  different  weather 
conditions.     In  general  the  proportions  of  nitrogen  and  oxygen, 
the  two  most  important  constituents  of  dry  air,  are  approximately 
as  follows : 

By  weight       By  volume 

Nitrogen 76.9  79.1 

Oxygen 23.1  20.9 

Carbon  dioxide  and  water  vapor  are  also  contained  in  air  in 
varying  amounts  and  there  are  in  addition  small  quantities  of 
other  gases,  such  as  argon,  ozone,  and  neon,  which  are  of  less 
importance.  Air  is  not  a  chemical  combination  but  is  a  mechan- 
ical mixture  of  these  gases. 

173.  Oxygen. — Oxygen,  (0),  which  constitutes  about  one-fifth 
of  the  air  by  volume,  is  the  element  upon  which  animal  life  is 
dependent  for  its  existence.     In  the  process  of  respiration  the 
lungs  draw  in  and  expel  periodically  a  small  quantity  of  air  and 
a  portion  of  the  oxygen  unites  chemically,  while  in  the  lungs, 
with  impurities  of  the  blood,  and  thereby  cleanses  it.     Some  of 
the  resulting  products  of  this  chemical  reaction  are  exhaled  in 
the  form  of  gases  and  vapors.     Our  health  and  bodily  comfort  are 
dependent  upon  the  proper  performance  of  this  process. 

174.  Nitrogen. — Nitrogen,  (N),  which  constitutes  nearly  all  of 
the  remaining  four-fifths  of  the  air  by  volume,  is  a  relatively 
inert  gas.     It  performs  the  important  function  of  diluting  the 
oxygen.     As  the  human  body  is  organized  this  dilution  is  essen- 
tial; an  atmosphere  of  pure  oxygen  would  soon  burn  up  and 
destroy  the  body  tissues. 

175.  Carbon  Dioxide. — Carbon  dioxide,  (C02),  exists  in  small 
amounts  in  the  open  air,  the  purest  air  containing  from  3  to  4  parts 
of  CO2  by  volume  in  10,000.     Carbon  dioxide  is  also  known  as  car- 
bonic acid  gas,  as  it  forms  a  weak  acid  when  dissolved  in  water. 
Being  one  of  the  products  of  respiration  it  is  found  in  larger 
quantities  in  the  air  of  occupied  rooms.     Carbon  dioxide  was 

196 


AIR  AND  ITS  PROPERTIES  197 

for  a  long  time  believed  to  have  a  poisonous  effect  when  taken 
into  the  lungs,  but  is  now  known  to  be  quite  harmless,  of  itself, 
even  in  appreciable  amounts.  It  has  the  effect,  however,  of 
diluting  the  oxygen  content  of  the  air.  This  necessitates  an 
increase  in  the  rate  of  breathing  and  under  extreme  conditions 
causes  great  discomfort.  Haldane  and  Priestly  found  that  with 
2  per  cent,  of  C02  the  lung  action  was  increased  50  per  cent.; 
with  3  per  cent,  of  C02  about  100  per  cent.;  with  4  per  cent,  of 
C02  about  200  per  cent.;  and  with  6  per  cent,  of  C02  about  500 
per  cent.  With  6  per  cent,  breathing  becomes  very  difficult, 
while  with  more  than  10  per  cent,  there  occurs  a  loss  of  con- 
sciousness, but  no  immediate  danger  to  life.  Exposure  to  an 
atmosphere  containing  even  25  per  cent,  of  CCh  does  not  result 
in  immediate  death. 

Being  a  product  of  respiration  the  amount  of  C02  present  in 
the  atmosphere  of  a  room  is  an  indication  of  the  amount  of  air 
being  supplied  to  the  room.  The  measurement  of  the  C02 
content  of  air  is  therefore  of  importance  in  ventilating  work. 
There  are  several  methods  of  measurement  in  use,  the  most 
accurate  of  which  is  that  devised  by  Petterson  and  Palmquist. 
The  apparatus  is  provided  with  a  graduated  chamber  into  which 
a  sample  of  air  is  drawn  and  measured.  It  is  then  made  to 
flow  into  a  burette  containing  a  saturated  solution  of  caustic 
potash  which  absorbs  the  C02-  The  air  is  then  forced  back  to 
the  measuring  chamber  and  the  decrease  in  volume  noted.  The 
apparatus  is  calibrated  to  read  directly  in  parts  per  10,000. 

Another  method  sometimes  used  is  that  of  Wolpert.  A  solu- 
tion of  sodium  carbonate  of  known  concentration  is  made  up 
and  a  small  quantity  of  phenolphthalein  indicator  is  mixed  with 
it.  A  suitable  piston  arrangement  is  used  to  force  a  known 
volume  of  the  air  to  be  analyzed  into  contact  with  the  solution 
and  the  apparatus  is  shaken  to  promote  the  reaction  between  the 
acid  C02  and  the  alkaline  solution.  The  process  is  repeated 
several  times  until  the  original  pink  color  of  the  solution  dis- 
appears. The  number  of  charges  of  air  necessary  to  cause  the 
color  change  gives  an  indication  of  its  CC>2  content. 

176.  Water  Vapor. — Water  vapor  is  an  important  constituent 
of  the  atmosphere.  It  is  the  most  variable  in  quantity  of 
any  of  the  atmospheric  elements,  its  amount  depending  largely 
on  the  weather  conditions.  In  the  northern  part  of  the  United 
States  the  range  of  the  moisture  content  of  the  atmosphere  is 


198  HEATING  AND  VENTILATION 

very  great.  In  New  York,  for  example,  it  varies  at  different 
times  from  0.5  grain  to  7  grains  per  cubic  foot.  Water  vapor, 
strictly  speaking,  is  nothing  other  than  steam  at  very  low  pressures, 
and  its  properties  are  similar  to  those  of  steam.  This  fact  should 
always  be  borne  in  mind  when  dealing  with  the  subject  of  atmos- 
pheric moisture.  Another  conception  that  should  be  thoroughly 
understood  is  that  of  Dalton's  law  of  partial  pressures.  Accord- 
ing to  this  law,  in  any  mechanical  mixture  of  gases,  each  gas  has 
a  partial  pressure  of  its  own  which  is  entirely  independent  of  the 
partial  pressures  of  the  other  gases.  For  example,  consider  a 
cubic  foot  of  hydrogen  gas  at  an  absolute  pressure  of  5  pounds 
per  square  inch.  If  a  cubic  foot  of  nitrogen  at  an  initial  pressure 
of  10  pounds  per  square  inch  be  injected  into  the  same  space, 
the  resulting  total  pressure  will  be  15  pounds  per  square  inch  and 
the  volume  1  cubic  foot.  In  air,  therefore,  the  oxygen,  nitrogen, 
water  vapor,  and  other  gases  each  have  their  own  partial  pressure, 
the  sum  of  all  of  them  being  equal  to  the  total  or  barometric 
pressure. 

For  every  temperature  there  is  a  corresponding  partial  pres- 
sure of  water  vapor  at  which  the  vapor  is  in  a  saturated  state, 
its  condition  then  being  exactly  similar  to  that  of  saturated  steam, 
i.e.,  with  the  maximum  number  of  molecules  occupying  a  unit 
space.  When  the  water  vapor  is  in  a  saturated  condition  the  air 
is  also  spoken  of  as  being  saturated  since  it  then  contains  the 
maximum  weight  of  vapor  which  it  can  hold  at  that  temperature. 
If  the  temperature  of  the  air  is  higher  than  that  corresponding  to 
the  partial  pressure  of  the  water  vapor,  the  vapor  is  superheated ; 
if  the  temperature  drops  below  the  saturation  point  some  of  the 
vapor  is  condensed  and  the  vapor  pressure  is  lowered  to  that 
corresponding  to  the  new  temperature.  The  saturation  tem- 
perature is  termed  the  dew  point.  The  partial  pressure  of 
saturated  vapor  increases  as  the  temperature  increases.  Conse- 
quently air  at  higher  temperatures  is  capable  of  holding  a  greater 
weight  of  water  per  cubic  foot.  It  should  be  remembered  that 
the  water  vapor  exists  independently  of  the  air  except  for  the  tem- 
perature effect  of  the  latter;  and  the  vapor  may  be  thought  of  as 
occupying  the  given  volume  at  its  own  partial  pressure.  The 
state  of  intimate  mixture  of  the  air  and  vapor  causes  their  tem- 
peratures to  be  always  the  same. 

177.  Relative  and  Absolute  Humidity. — Atmospheric  mois- 
ture is  termed  humidity.  Absolute  humidity  is  the  actual 


AIR  AND  ITS  PROPERTIES  199 

vapor  content  expressed  in  grains  per  cubic  foot  or  per  pound 
of  air.  The  ratio  of  the  vapor  content  to  the  vapor  content 
of  saturated  air  at  the  same  temperature,  expressed  in  per 
cent.,  is  called  the  relative  humidity.  For  example,  given  a  sam- 
ple of  air  at  70°  having  an  absolute  humidity  of  4  grains  per 
cubic  foot.  Since  saturated  air  at  70°  contains  8  grains  per 
cubic  foot,  the  relative  humidity  is  50  per  cent. 

178.  Total  Heat  of  Air.— The  total  heat  above  0°  of  air  con- 
taining aqueous  vapor  is  the  sum  of  the  heat  of  the  air  and 
the  heat  of  the  vapor.     The  latter  has  three  components:  the 
heat  of  the  liquid,  the  heat  of  vaporization,  and  the  superheat. 
The  vapor  is  always  in  a  superheated  condition  unless  the  air  is  at 
the  saturation  point. 

In  dealing  with  air  containing  vapor  it  is  often  convenient  to 
use  the  units  of  weight  instead  of  volume  as  a  basis  for  calcula- 
tions. The  total  heat  above  0°  in  1  pound  of  dry  air  at  tempera- 
ture ta  is  equal  to 

H  -  Cpa(ta  -  0) 

in  which  ta  is  the  air  temperature  and  Cpa  =  0.2415.,  the  specific 
heat  of  air  at  constant  pressure. 

Let  Ww  =  the  weight  of  water  vapor  contained  in  1  pound  of  a 
mixture  of  air  and  water  vapor.  Then  for  saturated  atmosphere 

H  =  (1  --  Ww)  X  Cpa(ta  -  0)  +  Ww(h'  +  r) 
in  which  h'  =  heat  of  the  liquid  above  0°  for  the  water  vapor 

r  =  latent  heat  of  the  water  vapor. 

For  atmosphere  below  saturation  (and  therefore  containing 
superheated  vapor)  at  temperature  ta 

H  =  (1  -  Ww)  X  Cpa(ta  -  0)  +  Ww(hr  +  r  +  C'ps(ta  -  td)) 
in  which  td  is  the  temperature  at  the  dew  point  and  C'ps  is  the 
specific  heat  of  water  vapor  at  constant  pressure. 

179.  Adiabatic    Saturation. — When   air   below    saturation   is 
brought  into  intimate   contact  with  water  there  is  always  a 
tendency  for  some  of  the  water  to  vaporize,  adding  to  the  mois- 
ture content  of  the  air.     If  no  heat  is  added  from  an  outside 
source  and  none  removed,  the  heat  of  vaporization  for  the  mois- 
ture which  is  added  will  be  supplied  entirely  at  the  expense  of 
the  heat  of  the  air  and  of  the  superheat  of  the  original  quantity 
of  water  vapor.,    The  process  will  continue  until  the  saturation 
point  is  reached.     A  process  of  this  nature  taking  place  without 


200  HEATING  AND  VENTILATION 

a  transfer  of  heat  to  or  from  an  outside  source  is  called  adiabatic 
and  the  final  temperature  which  is  reached  is  therefore  termed 
the  temperature  of  adiabatic  saturation  or  wet-bulb  temperature. 
Its  depression  below  the  original  temperature  of  the  air  will 
depend  upon  the  amount  of  moisture  which  was  added  to  bring 
the  air  to  saturation.  If  the  air  is  saturated,  no  moisture  can  be 
added,  and  the  wet-bulb  and  dry-bulb  temperatures  coincide. 
The  heat  used  in  the  vaporization  of  the  moisture  which  was 
added  is  exactly  equal  to  the  heat  given  up  by  the  air  and  by 
the  water  vapor  which  it  contained  originally,  assuming  that 
the  water  which  was  added  was  at  the  temperature  of  adiabatic 
saturation.  The  action  may  be  expressed  algebraically  as 
follows:1 

Let     t  =  temperature  of  the  air. 

t'  =  temperature  of  adiabatic  saturation. 
W  =  weight  of  water  vapor  mixed  with  1  pound  of  dry 

air  at  saturation  at  temperature  t'. 
W  =  weight  of  water  vapor  mixed  with  1  pound  dry  air 

at  temperature  t. 
W    -  W  =  weight  of  water  added  per  pound  of  dry  air. 

r  =  latent  heat  of  vaporization  at  temperature  t. 
CP8  =  specific  h^at  of  water  vapor  at  constant  pressure. 
Cpa  =  specific  heat  of  dry  air  at  constant  pressure. 

(W  -  W)r  =  CpsW(t  -  O  +  Cpa(t  -  t')  (1) 

W  =  rW'  ~  C*«(t  ~  V  (2} 

r  +  Cp8(t  -  t') 

180.  Measurement  of  Humidity. — The  principle  stated  in  the 
preceding  paragraph  affords  a  convenient  means  for  measuring 
humidity,  through  the  use  of  the  wet-  and  dry-bulb  ther- 
mometer. The  instrument  consists  of  two  mercury  thermome- 
eters,  the  bulb  of  one  of  which  is  covered  with  cotton  wicking. 
The  end  of  the  wicking  extends  into  a  bottle  of  water  and  the 
entire  length  is  kept  wet  by  absorption.  As  the  water  is  evapo- 
rated from  the  wicking  its  temperature  is  lowered  to  the  tem- 
perature of  adiabatic  saturation  or  "wet-bulb"  temperature. 
By  reading  both  thermometers  when  they  have  reached  a  con- 
stant point  the  wet-bulb  depression  is  obtained  and  the  moisture 
content  of  the  air  (W)  can  be  found  from  equation  (2),  Par.  179. 

1  From  "Rational  Psychrometric  Formulae,"  W.  H.  CARRIER,  Trans. 
A.  S.  M.  E.,  1911. 


AIR  AND  ITS  PROPERTIES 


201 


Distinction  should  be  drawn  between  the  wet-bulb  temperature 
and  the  dew  point,  which  was  denned  in  Par.  176.  The  former 
temperature  is  produced  by  adding  moisture  to  the  air  and  causing 
its  temperature  to  drop  by  reason  of  the  giving  up  of  heat  to 
vaporize  the  water.  The  dew  point,  on  the  other  hand,  is  reached 
by  removing  heat  from  the  air  without 
changing  its  moisture  content.  In  order 
to  obtain  accurate  results  with  a  wet- 
bulb  thermometer  it  is  necessary  that 
the  air  surrounding  the  wet  bulb  be  in 
motion  so  that  the  maximum  evapo- 
ration may  be  secured.  For  this  reason 
the  best  form  of  wet-  and  dry-bulb 
thermometer  is  the  "  sling  psychro- 
meter" illustrated  in  Fig.  147.  In  this 
instrument  the  wet-  and  dry-bulb 
thermometers  are  mounted  on  a  metal 
strip  pivotted  to  a  handle.  In  using 
the  instrument  the  wick  surrounding 
the  wet  bulb  is  moistened  and  the  in- 
strument is  whirled  rapidly  and  read  at 
intervals  until  there  is  no  further  drop 
in  the  wet-bulb  temperature.  Somewhat 
more  accurate  results  are  obtained  with 
the  " aspiration"  psychrometer  in  which 
a  continuous  current  of  air  is  drawn  over 
the  wet-bulb  thermometer  by  means  of 
a  small  fan  driven  by  clockwork. 

It  is  necessary  that  the  water  used  to 
moisten  the  wet  bulb  of  the  sling  psy- 
chrometer be  at  approximately  the  wet- 
bulb   temperature;   otherwise  the  time   required  to  bring  the 
water  to  the  wet-bulb  temperature  might  be  so  great  that  parts 
of  the  wicking  would  become  dry. 

The  ideal  psychrometric  chart  in  Fig.  148  is  constructed  for  use 
with  the  sling  psychrometer.1  This  chart  gives  the  moisture 
content  of  air  in  grains  per  cubic  foot,  the  volume  basis  being  the 
more  convenient  for  ordinary  ventilating  work.  In  Figs.  I  and 
II,  in  the  Appendix,  are  given  the  psychrometric  charts  which 
give  the  properties  of  air  on  the  basis  of  1  pound  of  air. 

1  From  "Fan  Engineering,"  Buffalo  Forge  Company. 


FIG.   147. — Sling  psychrom- 
eter. 


202 


HEATING  AND  VENTILATION 


181.  Example  of  Use  of  Psychrometric  Chart. — Given  a 
dry-bulb  temperature  of  80°  and  a  wet-bulb  temperature  of  70°, 
find  the  relative  and  absolute  humidity  and  the  dew  point. 
From  the  80°  point  on  the  horizontal  scale  follow  the  vertical 
line  to  its  intersection  with  the  diagonal  line  representing  the 
wet-bulb  temperature  of  70°.  Passing  horizontally  to  the  left 
from  this  point  to  the  left-hand  scale  we  find  that  the  absolute 
humidity  is  6.65  grains  per  cubic  foot.  To  find  the  relative 
humidity  we  note  that  this  same  point  lies  between  the  60  and 


100*  90#  80*    70# 


25      30     35     40      45     50     55     60     65     70     75     80     85 

Dry  Bulb  Temperature 
FIG.  148.  —  Psychrometric  chart. 


90     95    100   J05 


70  per  cent,  relative  humidity  lines  (the  curved  lines  extending 
upward  to  the  right)  and  that  the  relative  humidity  is  62  per  cent. 
To  find  the  dew  point,  follow  left  horizontally  from  this  same 
point  to  the  curved  line  of  wet-bulb  temperatures,  called  the 
saturation  line.  The  dew  point  is  64.5°. 

The  relation  between  the  wet-  and  dry-bulb  temperatures  and 
the  dew  point  should  be  thoroughly  understood. 

182.  Application  to  Air  Conditioning.  —  If  water  is  sprayed 
continuously  into  the  path  of  a  current  of  air  and  the  same  water 
is  recirculated  repeatedly  the  temperature  of  the  water  will 
approach  the  wet-bulb  temperature  of  the  air.  The  latter  will 
not  change  as  the  air  passes  through  the  water  spray  but  the  dry- 


AIR  AND  ITS  PROPERTIES 


203 


bulb  temperature  of  the  air  will  be  lowered  until  it  approaches 
the  wet-bulb  temperature,  and  at  saturation  the  two  will  coincide. 
The  wet-bulb  temperature  depends  upon  the  total  heat  of  the  air  and 
vapor  and  will  be  constant  so  long  as  the  total  heat  of  the  mixture  of 
air  and  vapor  is  constant.  In  the  process  mentioned  the  heat  of 
the  air  above  the  wet-bulb  temperature  and  the  superheat  of  its 

TABLE  XXXVII. — PROPERTIES  OF  DRY  Am1 
Barometric  Pressure  29.921  Inches 


Tem- 
per- 
ature, 

dR' 

Weight 
per 
cu.  ft., 
pounds 

Ratio 
to 
volume 
at  70° 
F. 

B.t.u. 
absorbed 
by  1  cu. 
ft.  dry 
air  per 
(teg.  F. 

Cu.  ft. 
dry  air 
warmed 
1°  per 
B.t.u. 

Tem- 
pera- 
ature, 
deg. 
F. 

Weight 
per 
cu.  ft., 
pounds 

Ratio 
to 
volume 
at  70° 
F. 

B.t.u. 
absorbed 
by  1  cu. 
ft.  dry 
air  per 
deg.  F. 

Cu.  ft. 
dry  air 
warmed 
l°per 
B.t.u. 

0 

0.08636 

0  .  8680 

0.02080 

48.08 

130 

0.06732 

1.1133 

0.01631 

61.32 

5 

0.08544 

0.8772 

0.02060 

48.55 

135 

0.06675 

1  .  1230 

0.01618 

61.81 

10 

0.08453 

0.8867 

0.02039 

49.05 

140 

0.06620 

1.1320 

0.01605 

62.31 

15 

0.08363 

0.8962 

0.02018 

49.56 

145 

0.06565 

1.1417 

0.01592 

62.82 

20 

0.08276 

0.9057 

0.01998 

50.05 

150 

0.06510 

1.1512 

0.01578 

63.37 

25 

0.08190 

0.9152 

0.01977 

50.58 

160 

0.06406 

1.1700 

0.01554 

64.35 

30 

0.08107 

0.9246 

0.01957 

51.10 

170 

0.06304 

1  .  1890 

0.01530 

65.36 

35 

0.08025 

0.9340 

0.01938 

51.60 

180 

0.06205 

1.2080 

0.01506 

66.40 

40 

0.07945 

0.9434 

0.01919 

52.11 

190 

0.06110 

1.2270 

0.01484 

67.40 

45 

0.07866 

0.9530 

0.01900 

52.64 

200 

0.06018 

1.2455 

0.01462 

68.41 

50 

0.07788 

0.9624 

0.01881 

53.17 

220 

0.05840 

1.2833 

0.01419 

70.48 

55 

0.07713 

0.9718 

0.01863 

53.68 

240 

0.05673 

1.3212 

0.01380 

72.46 

60 

0.07640 

0.9811 

0.01846 

54.18 

260 

0.05516 

1.3590 

0.01343 

74.46 

65 

0.07567 

0.9905 

0.01829 

54.68 

280 

0.05367 

1.3967 

0.01308 

76.46 

70 

0.07495 

1.0000 

0.01812 

55.19 

300 

0.05225 

1.4345 

0.01274 

78.50 

75 

0.07424 

1.0095 

0.01795 

55.72 

350 

0.04903 

1  .  5288 

0.01197 

83.55 

80 

0.07356 

.0190 

0.01779 

56.21 

'      400 

0.04618 

1  .  6230 

0.01130 

88.50 

85 

0.07289 

.0283 

0.01763 

56.72 

450 

0.04364 

1.7177 

0.01070 

93.46 

90 

0.07222 

.0880 

0.01747 

57.25 

500 

0.04138 

1.8113 

0.01018 

98.24 

95 

0.07157 

.0472 

0.01732 

57.74 

550 

0.03932 

1.9060 

0.00967 

103.42 

100 

0.07093 

.0570 

0.01716 

58.28 

600 

0.03746 

2.0010 

0.00923 

108.35 

105 

0.07030 

.0660 

0.01702 

58.76 

700 

0.03423 

2.1900 

0.00847 

118.07 

110 

0.06968 

.0756 

0.01687 

59.28 

800 

0.03151 

2.3785 

0.00782 

127.88 

115 

0.06908 

.0850 

0.01673 

59.78 

900 

0.02920 

2.5670 

0.00728 

137.37 

120 

0.06848 

.0945 

0.01659 

60.28 

1000 

0.02720 

2.7560 

0.00680 

147.07 

125 

0.06790 

.1040 

0.01645 

60.79 

1200 

0.02392 

3.1335 

0.00603 

165.83 

original  water  vapor  content  go  to  supply  the  heat  of  vaporiza. 
tion  for  the  added  moisture,  as  expressed  by  equation  (1),  Par- 
179.  This  means  is  often  employed  to  cool  the  air  for  ventilation. 
If  a  spray  of  artificially  cooled  water  be  used  the  air  can  be 
cooled  to  within  a  few  degrees  of  the  water  temperature.  If  this 

1  From  "Fan  Engineering,"  Buffalo  Forge  Company. 


204 


HEATING  AND  VENTILATION 


temperature  is  below  the  dew  point  of  the  air  some  of  the  moisture 
content  will  be  condensed  and  the  resulting  condition  will  be  one 
of  saturation  at  the  final  temperature.  These  principles  are 
applied  practically  in  the  cooling  and  dehumidifying  of  air  which 
will  be  discussed  in  Chapter  XVII. 

183.  Properties  of  Dry  and  Saturated  Air. — The  properties 
of  dry  air  are  given  in  Table  XXXVII  and  the  properties  of  satu- 
rated air  in  Table  XXXVIII  at  the  standard  barometric  pressure 
of  29.92  inches  of  mercury. 


TABLE  XXXVIII. — PROPERTIES  OF  SATURATED  Am1 
Weights  of  Air,  Vapor  of  Water,  and  Saturated  Mixture  of  Air  and  Vapor  at 
Different  Temperatures,  Under  Standard  Atmospheric  Pressure 
of  29.921  Inches  of  Mercury 


Temper- 
ature, 
deg.  F. 

Vapor  pres- 
sure, inches 
of  mercury 

Weight  in  a  cu.  ft.  of  mixture 

B.t.u.  ab- 
sorbed  by 
1  cu.  ft. 
sat.  air  per 
deg.  F. 

Cubic  feet 
sat.  air 
warmed  1° 
per  B.t.u. 

Weight  of 
the    dry 
air,  pounds 

Weight  of 
the   vapor, 
pounds 

Total  weight 
of  the 
mixture, 
pounds 

0 

0.0383 

0.08625 

0.000069 

0.08632 

0.02082 

48.04 

10 

0.0631 

0.08433 

0.000111 

0.08444 

0.02039 

49.05 

20 

0.1030 

0.08247 

0.000177 

0.08265 

0.01998 

50.05 

30 

0.1640 

0.08063 

0.000276 

0.08091 

0.01955 

51.15 

40 

0.2477 

0.07880 

0.000409 

0.07921 

0.01921 

52.06 

50 

0.3625 

0.07694 

0.000587 

0.07753 

0.01883 

53.11 

60 

0.5220 

0.07506 

0.000829 

0.07589 

0.01852 

54.00 

70 

0.7390 

0.07310 

0.001152 

0.07425 

0.01811 

55.22 

80 

1.0290 

0.07095 

0.001576 

0.07253 

0.01788 

55.93 

90 

1.4170 

0.06881 

0.002132 

0.07094 

0.01763 

56.72 

LOO 

1.9260 

0.06637 

0.002848 

0.06922 

0.01737 

57.57 

110 

2.5890 

0.06367 

0.003763 

0.06743 

0.01716 

58.27 

120 

3.4380 

0.06062 

0.004914 

0.06553 

0.01696 

58.96 

130 

4.5200 

0.05716 

0.006357 

0.06352 

0.01681 

59.50 

140 

5.8800 

0.05319 

0.008140 

0.06133 

0.01669 

59.92 

150 

7.5700 

0.04864 

0  010310 

0.05894 

0.01663 

60.14 

160 

9.6500 

0.04341 

0.012956 

0.05637 

0.01664 

60.10 

170 

12.2000 

0.03735 

0.016140 

0.05349 

0.01671 

59.85 

180 

15.2900 

0.03035 

0.019940 

0.05029 

0.01682 

59.45 

190 

19.0200 

0.02227 

0.024465 

0.04674 

0.01706 

58.80 

200 

23.4700 

0.01297 

0  .  029780 

0.04275 

0.01750 

57.15 

From  "Fan  Engineering,"  Buffalo  Forge  Company. 


AIR  AND  ITS  PROPERTIES  205 

184.  Specific  Heat  of  Air. — The  specific  heat  of  a  gas  may  be 
expressed  in  either  of  two  ways:  i.e.,  the  specific  heat  of  constant 
pressure,  and  the  specific  heat  of  constant  volume.  The  reason 
for  this  has  already  been  stated  (Par.  6).  In  ventilating  work 
the  former  quantity  is  the  one  involved.  Its  value  as  determined 
by  Carrier  is  0.2415  B.t.u. 

Problems 

1.  Given  wet-bulb  temperature  66°,  dry-bulb  temperature  80°.     Find 
dew  point,  per  cent,  saturation,  and  moisture  content. 

2.  Given  air  at  a  temperature  of  60°  and  containing  5  grains  of  water 
vapor  per  cubic  foot.     What  is  its  relative  humidity? 

3.  The  air  outside  of  a  building  is  at  a  temperature  of  31°  and  has  a  rela- 
tive humidity  of  84  per  cent.     On  being  drawn  into  the  building  it  is  heated 
to  70°.     What  is  its  relative  humidity  at  the  higher  temperature? 

4.  Air  at  80°  is  87  per  cent,  saturated.     When  cooled  to  55°  what  is  its 
new  moisture  content? 

5.  Air  at  25°  has  a  humidity  of  90  per  cent.     How  much  moisture  must 
be  added  to  give  it  a  humidity  of  50  per  cent,  when  heated  to  70°? 


CHAPTER  XIV 
VENTILATION 

185.  Ventilation  Requirements. — Ventilation  may  be  defined 
as  the  science  of  maintaining  atmospheric  conditions  which  are 
comfortable  and  healthful  to  the  human  body.  The  effect  of 
civilization  in  causing  mankind  to  remain  indoors  for  long  periods 
has  made  proper  ventilation  of  great  and  increasing  importance. 

The  science  of  ventilation  has  only  recently  approached  a 
satisfactory  stage.  The  difficulty  has  been  not  one  of  providing 
the  proper  mechanical  equipment  but  of  learning  what  condi- 
tions are  necessary  for  good  ventilation  and  of  establishing  the 
proper  standards  to  be  attained.  It  is  only  very  recently  that 
the  physiological  effects  of  certain  atmospheric  conditions  have 
been  understood,  and  the  quantitative  measurement  of  others 
and  the  knowledge  of  permissible  limits  are  still  lacking. 

The  atmosphere  affects  the  human  body  in  two  ways.  Por- 
tions of  the  surrounding  air  are  being  continually  drawn  into 
the  lungs  and  expelled  and  certain  qualities  of  the  atmosphere 
such  as  odors,  dust,  bacteria,  and  other  injurious  substances 
affect  the  respiratory  organs.  The  degree  of  humidity  of  the 
air  also  has  an  effect  on  the  respiratory  passages.  Secondly, 
the  condition  of  the  atmosphere  has  an  important  effect  on  the 
surface  of  the  body,  for  the  temperature,  degree  of  humidity, 
and  amount  of  air  motion  govern  the  rate  at  which  heat  is  dissi- 
pated from  the  skin — a  most  important  factor  in  bodily  comfort. 

To  sum  up,  the  following  factors  must  be  taken  into  account 
in  providing  proper  ventilation: 

1.  Amount  and  distribution  of  air  supply 

2.  Temperature 

3.  Humidity 

4.  Motion 

5.  Odors 

6.  Dust 

7.  Bacteria 

8.  Other  injurious  substances 

200 


VENTILATION  207 

Ventilation,  as  the  term  is  commonly  used,  refers  primarily 
to  the  effect  of  atmospheric  conditions  on  the  human  body. 
The  condition  of  the  atmosphere  is  regulated  in  many  manu- 
facturing processes  from  a  purely  manufacturing  standpoint 
and  without  particular  references  to  the  factors  mentioned 
above  as  they  affect  the  human  body.  This  is  usually  termed 
"air  conditioning." 

186.  Sources  of  Air  Pollution. — The  percentage  of  oxygen  in 
the  atmosphere  necessary  for  the  support  of  human  life  has  been 
shown  to  be  quite  low,  and  a  considerable  reduction  may  take 
place  without  even  causing  great  discomfort.  In  general,  it 
may  be  stated  that  the  quantity  of  air  to  be  supplied  for  proper 
ventilation  is  governed  by  other  factors  which  necessitate  a 
greater  quantity  than  that  required  to  maintain  a  sufficient 
oxygen  content. 

The  air  of  occupied  rooms  becomes  the  recipient  of  many 
polluting  elements,  the  most  important  of  which  are  the  prod- 
ucts of  respiration.  The  average  person  breathes  at  the  rate  of 
about  17  respirations  per  minute  while  at  rest.  At  each  respira- 
tion, about  30)^2  cubic  inches  of  air  are  inhaled  or  about  18 
cubic  feet  per  hour,  which  amounts  to  about  34  pounds  of  air 
in  24  hours  or  a  little  over  7  pounds  of  oxgyen.  The  inhaled 
air  loses  about  5  per  cent,  of  its  oxygen  content  while  in  the 
lungs  and  gains  from  3J^  to  4  per  cent,  of  carbon  dioxide.  The 
percentage  composition  of  free  air  and  of  expired  air,  by  volume, 
is  about  as  follows: 


Free  atmosphere, 
per  cent, 
(approximately) 

Expired  air, 
per  cent, 
(approximately) 

Oxygen  .  . 

20    9 

15  4 

Nitrogen  .  . 

79    1 

7Q  2 

Carbon  dioxide 

0  03  to  0  04 

4  03  to  4  04 

Ordinarily  there  is  not  enough  carbon  dioxide  in  the  air  of 
even  poorly  ventilated  rooms  to  be  harmful.  Its  amount  is 
merely  an  indication  of  the  quantity  of  air  being  supplied. 

Water  vapor  is  also  an  important  product  of  respiration. 
The  moisture  thus  added  to  the  air  will  increase  the  humidity 
above  the  comfort  point  unless  the  atmosphere  is  renewed  with 
sufficient  frequency. 


208 


HEATING  AND  VENTILATION 


There  are  also  emanations  from  the  mouth,  lungs,  and  skin 
which  give  rise  to  disagreeable  odors  and  which  are  believed  by 
some  to  have  a  poisonous  effect  when  taken  into  the  lungs. 
Although  this  belief  is  not  widely  accepted,  and  although  the 
exact  effect  of  this  organic  matter  is  not  known,  common  clean- 

TABLE  XXXIX. — AIR  SUPPLIED  TO  VARIOUS  CLASSES  OF  BUILDINGS 


Cubic  feet  per  hour 
per  occupant 

No.  of  renewals 
of  air  per  hour 

Churches,  auditoriums  and  assembly  rooms  .  . 
Theatres.  .           .                               ... 

1,200-1,800 
600-900 

Grade  schools 

1  000-1  500 

High  schools  
College  class  rooms 

1,800-2,000 
1,500-2,000 

Hospitals  for  ordinary  di  oa*os  
Hospitals  for  children  
Hospitals  for  contagious  diseases  
Hospitals  for  wounded  
Barracks      

2,500-3,500 
2,000-2,500 
5,000-5,500 
3,500-5,000 
1,000-1,800 

Living  rooms  in  residences 

1,200 

1-2 

Stairways  and  halls  
Bedrooms  
Work  shops  

600 
1,000 
600-2,000 

H-l 
IH 

Public  waiting  rooms 

4 

Public  toilet  rooms  .  .                       .        

20 

Small  convention  halls 

4 

General  offices 

3 

Private  offices  
Public  dining  rooms 

4 
4 

Banquet  halls 

5 

Basement  restaurants  ....        ...            ... 

8-12 

Hotel  kitchens 

10-20 

Public  libraries  

3 

Textile  mills 

4 

Engine  rooms 

10-20 

Boiler  rooms.        .                .    .          

10-20 

Railroad  roundhouses  

12 

liness  alone  demands  that  sufficient  fresh  air  be  supplied  to  dilute 
such  impurities  considerably.  The  dilution  of  the  bacteria 
in  the  expired  air  is  also  of  some  value  in  reducing  contagion. 
There  are  other  sources  of  air  pollution,  such  as  the  products 
given  off  by  the  combustion  in  gas  and  oil  lamps  and  from 
manufacturing  processes.  Gas  lights  give  off  carbon  dioxide, 


VENTILATION  209 

water  vapor,  and  traces  of  sulphuric  acid.  If  the  burners  are 
not  properly  adjusted,  carbon  monoxide,  which  has  a  poisonous 
and  sometimes  a  fatal  effect,  may  also  be  generated. 

Manufacturing  and  chemical  processes  give  off  various  gase- 
ous impurities,  but  such  conditions  require  individual  study  and 
no  set  rules  can  be  given. 

187.  Amount  of  Air  Required. — The  proper  amount  of  air 
supply  has  been  determined  from  experience  for  different  classes 
of  buildings.     For  buildings  such  as  theatres  and  schools,  it  is 
customary  to  provide  a  certain  volume  of  air  per  minute  for  each 
occupant.     For  rooms  where  the  number  of  occupants  is  vari- 
able or  where  there  is  pollution  from  sources  other  than  respira- 
tion, sufficient  fresh  air  is  provided  to  renew  that  in  the  room  a 
certain  number  of  times  per  hour.     For  ordinary  conditions  of 
temperature   and   humidity,   Table   XXXIX   gives   the   usual 
practice  as  to  the  amount  supplied. 

188.  Methods  of  Measuring  Air  Supply. — When  the  air  enters 
a  room  through  but  one  or  two  ducts,  the  quantity  can  be 
directly  measured  by  a  pitot  tube  or  anemometer,  the  use  of 
which  will  be  discussed  in  Chapter  XV.     Another  method  which 
in  many  cases  is  more  convenient  is  based  on  the  measurement 
of  the   carbon   dioxide   content   of  the   air   combined   with   a 
knowledge  of  the  rate  at  which  the  carbon  dioxide  is  added  by 
the  exhalation  from  the  occupants. 

If  it  be  assumed  that  each  person  produces  0.6  cubic  feet  of 
CO  2  per  hour,  then  ' 

6000 


1C.F.H. 


CO,-  X 


1  Let  V  =  volume   of  air  admitted  to  the  room  in  cubic  feet  per  hour. 
a  =  volume  of  CO2  contained  in  a  unit  volume  of  the  air  admitted. 
TI  =  amount  of  CO2  per  unit  volume  of  air  in  the  room  at  the  begin- 
ning of  the  test. 
r2  =  amount  of  CO2  per  unit  volume  of  air  in  the  room  at  the  end  of 

the  test. 
r  =  amount  of  CO2  per  unit  volume  of  air  in  the  room  at  any  time 

during  the  test. 

R  =  volume  of  room  in  cubic  feet. 

c  =  amount  of  CO2  produced  in  the  room,  in  cubic  feet  per  hour. 
t  =  time  of  experiment  in  hours. 

During  any  small  period  of  time  dt,  the  amount  of  air  entering  the  room 
is  Vdt  and  the  amount  of  CO2  contained  in  the  entering  air  is  aVdt.     The 
amount  of  CO2  produced  during  the  time  dt  is  cdt.     During  the  same  interval, 
14 


210  HEATING  AND  VENTILATION 

in  which 

C.F.H.  =  cubic  feet  of  air  per  hour  supplied  to  the  room  per 

occupant. 
CO 2.  =  carbon  dioxide   content  of  room  air  in  parts  per 

10,000. 
X  =  carbon  dioxide  content  of  outside  air  in  parts  per 

10,000  (usually  assumed  as  4). 

This  formula  is  recommended  by  Dr.  E.  V.  Hill  and  is  used  by 
the  Health  Department  of  the  City  of  Chicago.  The  chart  in 
Fig.  149  shows  the  air  supply  per  person  when  any  given  CO2 
content  exists  in  the  room.  The  above  method  of  determining 

an  equal  volume  Vdt  leaves  the  room  through  the  exhaust  flues  and  its  CC>2 
content  is  rVdt.     The  net  increase  in  the  volume  of  CO2  in  the  room  is  then 

(aV  +  c)dt  -  rVdt  =  (aV  -  rV  +  c)dt 

Let  the  increase  in  the  CO2  content  of  the  air  in  the  room  per  cubic  foot 
during  the  interval  dt  be  represented  by  dr.  Then  the  total  net  increase 
is  Rdr.  Equating  the  two 

Rdr  =  (aV  -rV  +  c}dt  (1) 

and 


r-  -  -         * 


aV  +  c  -  Vr 

-c-Vr) 

_  R         Vn  -aV  -c 
~  v  °ge  Vr2  -aV  -  c 

V  =  2.303  y  log™  yp-jj  -^  ~_Cc  (3) 

If  7*1  —  7*2,  which  means  that  there  is  no  increase  in  the  CC>2  content  of  the 
air  in  the  room,  then  the  amount  entering  the  room,  plus  the  amount  pro- 
duced must  equal  the  amount  leaving  the  room,  or 

aV  +  c  =  Vr2 
from  which 

V  =  rr-ir^  and  7*2  =  7*1  =  a  +  ^  (4) 

If  c  =0,  then  from  (3)  V  =  2.303  -  logio Tl  ~  a  (5) 

t  7*2   —  O, 

Equation  (4)  is  applied  practically  by  assuming  a  certain  production  of 
CO2  per  hour  per  person,  which  figure  is  usually  taken  as  0.6  cubic  foot. 
Equation  (4)  then  becomes 

6000 


VENTILA  TION 


211 


the  air  supply  does  not  apply  when  there  is  any  source  of  carbon 
dioxide  other  than  the  lungs  of  the  occupants. 

189.  Air  Distribution. — Merely  to  supply  enough  air  to  a  room 
is  not  sufficient  for  good  ventilation;  it  must  be  distributed  in 
a  fairly  uniform  manner  so  that  each  occupant  receives  approxi- 
mately the  specified  amount.  The  methods  of  distribution  will 
be  dealt  with  later.  To  determine  the  uniformity  of  distribu- 
tion, the  common  method  is  to  take  measurements  of  the  C02 
content  in  different  parts  of  the  room  and  thus  determine 
the  variation  of  the  quantity  supplied  per  occupant  at  the 
different  points  from  the  average  quantity. 


ibic  Ft.  of  Air  Supplied  per  Hr.  per  Person 

Formula  CO  2 
Transposed  ' 

X  may  be  ta 
of  outside 

6000 

CFH  per  oc 
jecomes  CFH  = 

icen  as  4  if  ai 
air  is  not  ma 

cupant  "*"•*• 
6000 

\ 

co2-x 

i  analysis 
de 

\ 

V 

^^^ 

~-  



.  

- 

== 

=^^MM 

50 


55 


GO 


O  5  10          15  20          25  30          35  40          45 

CO2 Content  in  10,000  Parts  of  Air 
FIG.   149. — Chart  showing  air  supply  per  person  for  various  amounts  of 


65 


190.  Temperature,  Humidity  and  Air  Motion. — The  removal 
of  heat  from  the  human  body  at  the  proper  rate  is  one  of  the 
essential  requirements  for  satisfactory  ventilation.  According 
to  Prof.  Foster  the  amount  of  heat  given  off  by  the  body  is  335 
to  460  B.t.u.  per  hour,  depending  upon  the  age,  sex,  diet,  exertion, 
etc.  About  15  B.t.u.  of  this  amount  are  carried  off  by  the  expired 
air  itself  and  35  B.t.u.  by  the  moisture  absorbed  from  the  lungs 
by  the  air.  Approximately  70  B.t.u.  are  removed  by  the  evapora- 
tion of  moisture  from  the  skin,  leaving  about  250  B.t.u.  to  be 
taken  care  of  by  radiation  and  convection  from  the  skin.  The 
two  latter  quantities  vary  considerably.  For  example  the  sur- 
rounding air  may  be  at  a  higher  temperature  than  the  body,  so 
that  no  heat  is  removed  by  radiation  or  convection  from  the 
skin  and  all  of  the  heat  must  be  removed  by  evaporation.  The 
temperature  regulating  mechanism  of  the  body  would  in  such  a 


212  HEATING  AND  VENTILATION 

case  cause  more  perspiration  to  be  produced  to  increase  the 
evaporative  cooling. 

The  amount  of  heat  carried  off  by  radiation  and  convection 
depends  upon  the  temperature  of  the  air  and  the  amount  of  its 
motion,  while  the  evaporative  cooling  effect  depends  upon  the 
amount  of  air  motion  and  upon  the  capacity  of  the  air  for  absorb- 
ing moisture.  The  moisture  absorbing  property  of  the  air, 
strictly  speaking,  depends  upon  the  difference  in  the  pressures 
of  the  water  vapor  in  the  air  and  at  the  surface  of  the  body. 
When  the  vapor  pressure  in  the  air  is  low  the  higher  vapor  pres- 
sure on  the  skin  causes  more  moisture  to  be  evaporated.  The 
relative  humidity  of  the  air  serves  as  an  approximate  index  of  its 
moisture  absorbing  power. 

When  the  air  is  stagnant,  a  layer  of  warm  moist  air  is  formed 
about  the  body  which  reduces  the  rate  of  heat  removal.  A  mod- 
erate amount  of  air  movement  augments  cooling,  both  by  con- 
vection and  evaporation,  through  replacing  this  envelope  with 
cooler  and  dryer  air. 

The  temperature,  humidity,  and  motion  of  the  air  are  thus 
very  important  factors  in  ventilation.  They  may  vary  within 
certain  limits  as  long  as  their  combined  effect  satisfies  the  re- 
quirements for  the  rate  of  heat  removal  from  the  body.  The 
sensations  of  drowsiness,  oppression,  and  headache  often  felt  in 
crowded  rooms  are  due  to  the  effect  of  heat  stagnation  on  the 
skin  rather  than  to  any  effect  of  the  atmosphere  on  the  lungs. 
This  has  been  demonstrated  by  various  experimenters  by  means 
of  tests  on  human  subjects  confined  in  air  tight  observation 
chambers.  After  the  subject  has  remained  in  such  a  chamber 
for  a  time  the  wet-bulb  temperature  rises  considerably  and 
great  discomfort  is  felt  which  is  not  relieved  by  breathing  air 
from  outside  through  a  tube,  but  which  is  greatly  mitigated  by 
stirring  up  the  air  in  the  chamber  by  electric  fans  and  thus 
increasing  the  cooling  power  of  the  atmosphere.  Other  subjects 
outside  of  the  chamber  feel  no  discomfort  on  breathing  air  from 
the  chamber  through  tubes. 

191.  The  Comfort  Zone. — The  relation  between  the  tempera- 
ture and  humidity  necessary  for  comfortable  conditions  is  shown 
by  the  chart  in  Fig.  150  which  was  constructed  by  Dr.  E.  V. 
Hill  from  a  series  of  tests  made  by  Prof.  J.  W.  Shepherd.  These 
tests  were  made  in  still  air  and  with  the  subjects  at  rest.  The 
dashed  line  drawn  through  the  center  of  the  comfort  zone  cord- 


VENTILATION 


213 


responds  very  closely  to  a  wet-bulb  temperature  of  56°.  It 
appears,  therefore,  that  for  still  air  and  when  no  physical  exertion 
is  being  undertaken,  a  wet-bulb  temperature  of  56°  produces 
comfortable  conditions.  Later  tests  have  established  the  wet- 
bulb  temperature  which  must  exist  with  various  rates  of  air 
motion  to  produce  conditions  of  comfort.  (See  Fig.  151,  p.  216.) 
The  wet-bulb  thermometer  is  without  a  doubt  a  more  accurate 
instrument  for  an  index  of  room  conditions  than  is  the  dry-bulb 
thermometer  which  is  commonly  used  for  the  purpose.  The 
humidity  of  the  inside  air  varies  as  does  that  of  the  outside  air, 
and  with  a  constant  dry-bulb  temperature  the  cooling  power  of 
the  air  will  vary  over  a  wide  range.  If,  on  the  other  hand,  the 
proper  wet-bulb  temperature  is  maintained,  the  cooling  power 
of  the  air  will  be  constant. 


55 


30   32    34    36   38 


68    70    72    74    76  78 


42    44    46    48    50    52    54    56    58   60    62    64 

Relative  Humidity  Per  Cent 

FIG.  150. — "Comfort  Zone"  showing  the  temperature  and  humidity  required 
to  produce  comfortable  conditions  in  still  air. 

192.  Air  Motion. — A  moderate  amount  of  air  movement  is 
desirable,  especially  in  crowded  rooms,  as  it  reduces  heat  stagna- 
tion by  changing  the  aerial  envelope  which  surrounds  the  body. 
The  velocity  of  movement  should  be  limited  to  not  more  than 
2  feet  per  second,  for  a  higher  velocity  is  uncomfortable.  In 
general,  a  movement  toward  the  face  is  preferable  to  a  movement 
from  the  rear.  In  a  room  supplied  with  fresh  air,  either  from 
open  windows  or  from  a  mechanical  ventilating  system,  there 
will  be  a  certain  amount  of  movement  of  the  air  caused  by  the 
introduction  of  fresh  air  and  the  removal  of  foul  air.  The  chill- 
ing effect  of  the  outside  walls  and  windows  and  the  convection 
currents  set  up  by  radiators  also  create  a  considerable  amount  of 
air  motion. 


214  HEATING  AND  VENTILATION 

Cubic  space  is  an  important  factor  in  ventilation.  When  a 
room  is  over-crowded  it  may  be  impossible  to  move  a  sufficient 
amount  of  air  through  it  without  causing  uncomfortable  drafts. 
Also  a  certain  amount  of  space  is  desirable  as  a  reservoir  of 
fresh  air  dilutes  the  products  of  respiration.  Dr.  Billings  recom- 
mends the  following  as  the  minimum  amount  of  space  to  be 
allowed  per  occupant. 

Cubic  feet  per  person 

Lodging  or  tenement  house 300 

School  room 250 

Hospital  ward 1,000-1,400 

Auditorium 200 

In  computing  the  cubic  space  for  this  purpose  all  space  over 
12  feet  from  the  floor  should  be  neglected. 

193.  Humidity. — The   humidity  of   the   atmosphere   has   an 
important  effect  on  the  respiratory  tractin  addition  to  its  bearing 
on  the  cooling  power  of  the  air.     When  the  cold  outside  air 
enters  a  building  by  infiltration  or  otherwise  and  is  heated  to 
room  temperature,  its  absolute  moisture  content  remains  the 
same,  but  its  relative  humidity  is  decreased  and  consequently 
its  capacity  for  absorbing  moisture  is  increased.     From  the  chart 
in  Fig.  1  of  the  Appendix  (p.  300)  we  see  that  air  at  20°,  containing 
12  grains  of  moisture  for  each  pound  of  dry  air,  has  a  relative 
humidity  of  about  80  per  cent.     If  its  temperature  is  raised  to  70° 
the  relative  humidity  is  lowered  to  approximately  13  per  cent. 
The  low  vapor  pressure  corresponding  to  this  condition  results  in 
an  increased  evaporation  of  moisture  from  surrounding  objects. 
The  dryness  of  the  air  which  prevails  in  most  buildings  during  the 
heating  season  has  an  extremely  bad  effect  on  the  respiratory 
tract.     The  mucous  membranes  lining  the  nasal  cavity  and  throat 
become  dry  and  irritated  and  especially  liable  to  infection.     The 
change  from  the  dry  indoor  air  to  the  mcist  outdoor  air  is  also 
believed  by  some  physiologists  to  be  deleterious. 

It  is  desirable  to  maintain  a  humidity  of  from  40  to  50  per  cent, 
under  average  conditions. 

194.  Odors. — Another  function  of  ventilation  is  the  removal 
or  reduction  of  odors,  the  most  common  of  which  arise  from 
human  bodies.     The  sources  of  these  odors  are  emanations  from 
the  mouth,  throat,  and  lungs,  the  perspiration  from  the  skin,  and 
soiled  clothing.     In  factories  there  are  odors  created  by  various 
manufacturing  processes. 


VENTILATION  215 

The  so-called  crowd  smell  is  not  harmful  of  itself,  for  it  has  been 
shown  that  healthful  existence  is  quite  possible  in  such  an  atmos- 
phere. Repulsive  odors  are  indirectly  harmful,  however,  in  that 
they  cause  the  occupants  of  the  room  to  breathe  less  deeply;  but 
regardless  of  their  actual  physiological  effect,  modern  standards  of 
cleanliness  require  that  sufficient  air  be  supplied  to  occupied 
rooms  to  maintain  a  wholesome  atmosphere. 

As  yet,  no  accurate  standard  has  been  found  for  the  measure- 
ment of  odors.  One  method  is  to  compare  the  odor  in  the  room 
with  a  number  of  odoriferous  solutions  of  varying  intensities. 
Sometimes  an  odor  may  be  nearly  imperceptible  as  such,  but 
may  still  impart  an  impression  of  stuffiness  to  the  atmosphere. 

195.  Dust  and  Bacteria. — The  air,  especially  that  of  cities, 
contains  a  large  amount  of  dust  in  very  finely  divided  particles. 
These  particles  consist  of  many  different  substances,  most  of 
which  are  mineral.     In  large  cities,  tons  of  cinders  and  smoke 
particles  are  cast  out  into  the  air  annually,  which  adds  to  the 
production  of  dust  from  other  sources.     Ordinary  dust  in  itself 
is  not  particularly  injurious  to  health  but  it  serves  as  a  carrying 
medium  for  all  sorts  of  bacteria.     There  are  some    industrial 
dusts  that  are  injurious  to  health  such  as  that  from  pearl  buttons, 
hair,  mineral  wool,  stone,  etc. 

Several  methods  of  determining  the  dust  content  of  air  have 
been  devised.  The  most  successful  scheme  is  to  draw  a  sample 
of  air  into  a  suitable  cylinder  containing  a  glass  disc  coated  with 
an  adhesive  varnish  and  so  placed  that  the  indrawn  air  impinges 
upon  it.  The  number  of  dust  particles  determined  by  micro- 
scopic count  affords  an  indication  of  the  amount  of  dust  in  the 
air.  Dust  can  be  quite  thoroughly  removed  from  air  by  means 
of  the  air  washer,  to  be  described  later. 

196.  Ventilation  Tests. — We  have  seen  that  good  ventilation 
demands  the  fulfillment  of  several  distinct  requirements.     Any 
adequate  method  of  testing  the  ventilation  of  a  room  must  (a) 
determine  the  degree  to  which  each  requirement  is  fulfilled  and 
(b)  combine  the  individual  results  to  show  how  nearly  the  ventila- 
tion of  the  room  approaches  what  is  known  as  perfect  ventila- 
tion.    The  synthetic  air  chart  devised  by  Dr.  E.  V.   Hill  and 
adopted  as  a  standard  by  the  American  Society  of  Heating  and 
Ventilating  Engineers  offers  a  means  of  determining  the  percent- 
age of  perfect  ventilation  by  considering  all  of  the  factors  involved. 
The  chart  is  shown  in  Fig.   151.     The  chart  contains  seven 


216  HEATING  AND  VENTILATION 


SYNTHETIC  AIR  CHART 

FOR  DETERMINING  THE  PERCENTAGE  OF  PERFECT  VENTILATION 


WET 

BULB 

DIFFERENCE 


DDST 

PAETICLES 
PER  CU.FOOT 


BACTERIA 

COLONIES 

TWO  MIN.PLATE 


ODORS 

PERCENT 
FREE  FROM 


C02 

PARTS  PER  10,000 


OTHER 
INJURIOUS 
SUBSTANCE 

) 


DISTRIB- 
UTION 
PERCENT 


PERCENT 
OF 

>ERFECT 


TO"  ~15T  15 


C.F.M.  -% 


54   15 


I3L  _ 


-SO"  T? 


85 


85 


50 


20 


—44— 


12 


CO 


12 


100,000 


100 


10 


10 


5° 


40 


90 


70 


70 


GO 


-24— 


-80- 


80 


50,000 


DO 


50 


95 


95 


"70~ 


80 


-14- 


90 


100. 


0  100 


100 


1 


I 


TEMPERATURE  HUMIDITY  AIR  MOTION 

BAROMETRIC  PRESSURE  29.92" 


100  150  200 

AIR  MOTION  FEET  PER  MINUTE 


FIG.  151. — The  synthetic  air  chart. 


VENTILATION  217 

vertical  columns,  one  for  each  of  the  various  factors  to  be  con- 
sidered and  a  column  in  which  all  of  the  results  are  summarized. 
The  base  of  each  column  represents  the  ideal  condition  or  100  per 
cent,  perfect.  Bordering  on  either  side  of  each  main  column  are 
two  narrow  columns  marked  "  —  %"  and  "  +  %."  The  former 
denotes  the  penalization  to  be  made  in  the  Per  cent,  of  Perfect 
column  for  that  particular  factor,  and  the  "  +  %"  denotes  the 
condition  considering  only  the  one  factor. 

The  various  factors  are  divided  into  three  groups  which  are 
separated  by  the  double  lines.  First,  Wet-Bulb  Difference, 
which  means  the  difference  between  the  actual  wet-bulb  tempera- 
ture and  the  ideal,  and  which  includes  the  factors  of  Tempera- 
ture, Humidity,  and  Air  Motion;  second,  Dust,  Bacteria,  and 
Odors;  third,  Carbon  Dioxide,  which  serves  as  an  indicator  of  the 
amount  of  air  supplied.  There  is  also  a  column  for  Other 
Injurious  Substances,  for  use  in  special  cases,  and  one  for  Distri- 
bution .  The  upper  limit  of  any  of  these  columns  represents  condi- 
tion where  life  would  be  impossible.  Hence  at  this  point  the 
"  ~  %"  column  would  indicate  100  per  cent,  penalization. 
(Since  the  upper  ends  of  the  columns  represent  conditions  not 
obtained  in  practice  they  are  not  included  in  the  chart.) 

To  illustrate  the  method  of  graduating  the  columns,  consider 
the  first  which  is  headed  Wet-Bulb  Difference.  When  at  rest 
with  no  air  motion,  the  ideal  wet-bulb  temperature  is  56°.  The 
upper  end  of  the  column  (not  shown)  represents  the  unlivable 
condition  which  is  approximately  106°  with  100  per  cent,  humidity 
or  a  wet-bulb  difference  of  50°.  Any  variation  from  56°  would 
therefore  represent  a  definite  percentage  of  variation  from  the 
ideal.  The  graduations  in  the  other  columns  were  constructed 
in  like  manner. 

After  the  values  of  all  the  factors  have  been  determined  by  test, 
the  results  are  shown  on  the  chart  by  a  heavy  vertical  line  (%  in. 
wide)  and  the  height  of  the  line  will  indicate  the  results  obtained 
in  the  test.  Penalizations  for  all  the  factors  may  then  be  read 
directly  opposite  the  top  of  each  line.  All  the  "  — %'s"  are 
then  totaled  and  the  sum  subtracted  from  100  per  cent,  to 
determine  the  per  cent,  of  perfect  ventilation  for  the  room  as  a 
whole.  This  result  is  plotted  in  the  last  column  headed  Per  cent, 
of  Perfect.  For  example,  if  the  sum  of  all  "  —  %'s"  found  in 
the  different  columns  is  15%  per  cent.,  then  the  difference 
between  100  and  15%,  or  84%  per  cent.,  is  plotted  in  the  last 


218  HEATING  AND  VENTILATION 

column  as  the  final  per  cent,  of  perfect  and  represents  the  quality 
of  the  ventilation  in  the  room. 

197.  Method  of  Making  Test. — Temperatures  and  humidities 
are  determined  with  a  sling  psychrometer.  The  velocity  and 
direction  of  air  movement  may  be  determined  by  timing  the 
passage  of  a  puff  of  smoke  or  vapor.  An  ammonium  chloride 
cloud  formed  by  the  simultaneous  production  and  mixing  of 
hydrochloric  acid  and  ammonium  vapors  is  generally  used. 

Dust  determinations  are  made  by  the  use  of  a  direct  counting 
instrument  as  described  in  Par.  195. 

Bacterial  determinations  should  be  made  in  accordance  with 
the  standard  adopted  by  the  American  Public  Health  Associa- 
tion. Petrii  dishes  4  inches  in  diameter  containing  standard 
agar  are  exposed  in  the  room  for  two  minutes.  They  are  then 
carefully  covered  and  incubated  for  48  hours,  after  which  the 
colonies  of  bacteria  are  counted. 

Odors  are  determined  in  accordance  with  the  following  rating : 

100  per  cent,  freedom  from  odors Perfect 

95  per  cent,  freedom  from  odors Very  faint 

90  per  cent,  freedom  from  odors Faint 

85  per  cent,  freedom  from  odors Noticeable 

80  per  cent,  freedom  from  odors Distinct 

75  per  cent,  freedom  from  odors Decided 

70  per  cent,  freedom  from  odors Strong 

The  determination  should  be  made  immediately  upon  going 
into  the  room  from  the  outer  air. 

For  carbon  dioxide  determinations  samples  are  taken  at 
various  stations  in  the  room.  The  best  method  is  to  use  120 
c.c.  bottles  and  to  fill  them  by  means  of  a  large  rubber  bulb 
which  is  inflated  by  a  pumping  bulb  until  it  holds  considerably 
more  air  than  the  volume  of  the  bottle.  The  air  is  then  allowed 
to  rush  into  the  bottle  and  displace  the  air  originally  in  it.  The 
operation  is  repeated,  care  being  taken  not  to  hold  the  apparatus 
where  the  air  expired  by  the  operator  will  be  drawn  in,  and  the 
bottle  is  then  carefully  sealed.  Analyses  are  made  with  a 
Peterson-Palmquist  instrument.  The  air  supply  may  be  deter- 
mined from  the  CC>2  readings  by  means  of  the  chart  in  Fig.  149. 
The  distribution  of  the  air  in  a  room  may  be  determined  from 
the  CC>2  readings  taken  in  the  various  parts  of  the  room.  The 
following  example  illustrates  the  method  of  calculating  the 


VENTILATION  219 

result.     Assume  four  samples  taken,  resulting  in  the  following 
analysis : 

Station  Parts  of  CO2  per  10,000 

1  6.4 

2  7.4 

3  9.2 

4  5.0 

Average  7.0 

The  variation  at  the  various  stations  above  or  below  the  average 
is  as  follows: 

Station 

1  7.0  -  6.4  =  0.6 

2  7.4  -  7.0  =  0.4 

3  9.2  -  7.0  =  2.2 

4  7.0  -  5.0  =  2.0 

Then  the  average  variation  from  the  average  C02  is  determined 
as  follows: 

0.6  +  0.4  +  2.2  +  2.0  _  1  f 

~^r 

The  percentage  of  variation  is  therefore  equal  to  1.3  -?-  7.0  = 
18.6  per  cent.  Therefore  the  percentage  distribution  =  100  — 
18.6  =  81.4  per  cent. 

The  column  headed  "Other  Injurious  Substances"  is  used  only 
in  special  cases  where,  owing  to  the  nature  of  the  processes 
carried  on,  some  particularly  injurious  substance  is  being  given 
off  to  the  air.  The  column  is  then  graduated,  consistent  with 
the  nature  of  the  substance. 

198.  Comfort  Chart. — The  inter-relation  of  temperature,  hu- 
midity, and  air  motion  is  shown  in  the  lower  portion  of  the 
chart.  The  intersection  of  the  Air  Motion  line  and  the  Physical 
State  line  determines  the  proper  wet-bulb  temperature.  This 
point  should  be  indicated  on  the  chart  by  a  small  angle  (thus  ~i) 
the  apex  of  the  angle  coinciding  with  the  point  of  intersection 
of  the  lines.  The  observed  dry  bulb'and  wet  bulb  is  also  indi- 
cated by  an  angle  (thus  i_).  The  difference  between  the  desir- 
able wet  bulb  and  the  observed  wet  bulb  is  plotted  in  the  first 
column  of  the  air  chart  marked  Wet-Bulb  Difference. 


220  HEATING  AND  VENTILATION 

199.  Recording  the  Results. — To  illustrate  the  method  of  deter- 
mining the  percentage  of  perfect  ventilation,  consider  the  results 
of  a  test  as  given  below : 

Dry-bulb  temperature 72° 

Wet-bulb  temperature 58° 

Air  Motion 20  ft.  per  minute 

Physical  state Light  work 

Dust 10,000  particles  per  cubic  foot 

Bacteria 10  colonies  on  a  2-minute  plate 

Odors 90  per  cent,  free  from 

CO2 7  parts  per  10,000 

Other  injurious  substances None 

Distribution 81.4 

These  values  are  now  represented  on  the  chart  by  a  %-in. 
vertical  line  drawn  in  the  center  of  each  of  the  respective  columns. 
The  proper  wet-bulb  temperature  is  determined  by  noting  the 
point  of  intersection  of  the  "light  work  line"  and  the  20-ft. 
air  motion  line;  this  is  55°  wet  bulb.  Since  the  actual  wet-bulb 
temperature  as  determined  by  the  test  is  58°  then  the  wet-bulb 
difference  is  3°.  This  value  is  plotted  in  the  first  column  and 
the  penalization  as  read  in  the  "  — %"  portion  is  —  5%  per 
cent.  For  the  10,000  particles  of  dust,  the  penalization  is  a 
—  1  per  cent.;  for  the  bacteria,  —1  per  cent.;  for  the  odors 
— 1^2  per  cent.;  for  the  COz  —  %  per  cent.;  for  other  injurious 
substances,  —0  per  cent.,  and  for  distribution  —  5%  per  cent. 
The  sum  of  all  these  penalizations  is  — 15%  per  cent.  Therefore 
the  per  cent,  of  perfect  ventilation  in  the  room  is  100  —  15%  = 
84%  per  cent.  This  value  is  then  plotted  in  the  last  column 
marked  Per  cent,  of  Perfect. 

200.  Ozone. — Ozone  is  used  to  some  extent  as  a  means  for 
counteracting  odors  and  bacteria.     Ozone  is  simply  a  form  of 
oxygen  in  which  the  molecule  consists  of  three  instead  of  two 
atoms.     The  additional  atom  is  readily  liberated  and  the  sub- 
stance  is   consequently  an   active   oxidizing   agent.     Ozone   is 
present  in  very  minute  amounts  in  the  atmosphere. 

When  injected  into  the  atmosphere  of  a  room  with  a  con- 
centration of  not  more  than  1  part  per  million,  ozone  is  capable 
of  obliterating  even  very  marked  odors.  The  exact  action  which 
takes  place  is  at  present  a  matter  of  debate.  By  some  it  is 
believed  that  ozone  actually  destroys  the  odors  through  its 
oxidizing  action.  It  is  known,  however,  that  it  is  quite  possible 


VENTILATION  221 

to  compensate  one  odor  with  another  so  that  its  effect  upon  the 
olfactory  membrane  is  neutralized,  and  it  may  be  that  the  real 
action  of  the  ozone  is  a  masking  of  the  odors  by  what  is  called 
olfactory  compensation  rather  than  a  destroying  of  them. 

It  is  very  essential  that  the  concentration  of  the  ozone  be 
kept  very  low,  for  in  an  atmosphere  of  more  than  about  1  part 
per  million  of  ozone,  serious  irritation  of  the  throat  and  lungs  is 
liable  to  result. 

The  common  method  of  producing  ozone  is  by  means  of  an 
electrical  discharge  at  high  voltage.  Several  commercial  ma- 
chines are  available  for  the  purpose. 

201.  Humidification. — Artificial  humidification  of  the   air  is 
generally  believed  to  be  desirable  in  nearly  every  class  of  build- 
ing.    There  is  no  doubt  but  that  the  dry  atmosphere  produced 
by  the  heating  up  of  the  cold  outer  air  is  detrimental  to  health 
by  rendering  the  respiratory  passages  more  liable  to  infection. 
Where    a   modern   ventilating   system    with    an   air  washer  is 
installed,  humidification  is  very  simply  and  satisfactorily  accom- 
plished but  in  buildings  not  so  equipped,   artificial  humidifi- 
cation is  more  difficult. 

Humidifiers  for  hot  air  furnaces  have  been  described  (Par. 
35,  p.  39).  In  rooms  heated  by  direct  radiation  there  are  several 
forms  of  humidifiers  which  may  be  used,  most  of  which  consist 
of  water  pans  of  some  sort  to  be  attached  to  the  radiator.  Very 
few  of  such  devices  are  really  successful,  however,  because  they 
do  not  evaporate  a  sufficient  quantity  of  water. 

Another  type  consists  of  a  small  bleeder  valve  which  admits 
steam  from  the  heating  system  directly  into  the  room.  Others 
inject  a  finely  divided  spray  of  water  into  the  air,  but  these 
devices  are  used  principally  in  connection  with  manufactur- 
ing processes. 

202.  Methods  of  Introducing  Air. — In  providing  ventilation 
for  a  room,  it  is  necessary  to  adopt  a  definite  scheme  for  the 
introduction  of  fresh  air  and  the  removal  of  the  vitiated  air. 
When  the  air  quantities  are  small  the  leakage  around  the  windows 
may  be  relied  upon  as  a  means  for  permitting  the  escape  of  the 
air^  but  in  general,  it  is  necessary  to  install  a  system  of  vent 
flues. 

There  are  two  general  methods  of  circulating  the  air  through 
a  room.  In  the  upward  system,  the  air  is  introduced  through 
the  floor  or  through  the  side  walls  near  the  floor  and  is  removed 


222 


HEATING  AND  VENTILATION 


near  the  ceiling.  In  the  downward  system,  the  air  is  introduced 
through  registers,  in  the  ceiling  or  in  the  side  walls  7  to  10  feet  above 
the  floor,  and  is  removed  near  the  floor.  The  former  method 
is  especially  adapted  to  theatres  and  auditoriums  where  a  large 
number  of  small  openings  can  be  provided  in  the  floor,  thus 
securing  a  very  even  distribution.  The  upward  system  is  also 
suitable  for  restaurants  and  rooms  where  there  is  smoking  or 
where  other  impurities  or  odors  are  created  which  have  a  natural 
tendency  to  rise.  The  downward  system  is  used  in  schools, 
hospitals,  etc.  where  it  is  not  practicable  to  have  openings  in 
the  floor. 


FIG.  152. — Effect  of  various  locations  of  inlet  and  outlet: 

The  relative  location  of  the  inlet  and  outlet  openings  affects  the 
thoroughness  of  the  air  renewal  throughout  the  room.  It  has 
been  demonstrated  that  the  most  effective  scheme  is  to  place 
the  outlet  near  the  floor  and  on  the  same  side  of  the  room  as  the 
inlet.  The  effect  of  various  locations  of  the  inlet  and  outlet  are 
shown  in  Fig.  152,  in  which  the  arrangement  d  is  in  general 
the  besjb. 

In  some  types  of  ventilating  systems  the  air  is  introduced 
at  approximately  the  room  temperature  and  at  a  sufficient 
velocity  to  distribute  itself  laterally  across  the  room.  Some- 
what better  distribution  can  usually  be  obtained,  however,  if 
the  air  is  introduced  at  somewhat  above  room  temperature.  It 
will  then  spread  out  in  a  layer  over  the  room  and  move  gradually 


VENTILATION  223 

downward  as  it  is  cooled  and  displaced  by  fresh  warmer  air 
from  above. 

Problems 

1.  A  test  made  in  a  room  in  which  there  are  several  people  shows  a  CO2 
content  of  12  parts  per  10,000.     What  quantity  of  air  is  being  supplied  per 
hour  per  occupant? 

2.  A  test  of  the  air  of  an  occupied  room  shows  a  CO2  content  of  13  parts 
per  10,000.     Outside  air  contains  3^  parts  per  10,000.     How  much  air  is 
being  supplied  per  hour  per  occupant? 

3.  A  ventilation  test  shows  the  following  results: 

Dry-bulb  temperature 70° 

Wet-bulb  temperature 53° 

Air  motion 50  feet  per  minute 

Physical  state At  rest 

Dust 20,000  particles  per  cubic  foot 

Bacteria 17  colonies 

Odors Very  faint 

CO2 6  parts  per  10,000 

Other  injurious  substances None 

Distribution 91.0  per  cent. 

What  per  cent,  of  perfect  is  the  ventilation? 

4.  The  outside  air  has  a  dry-bulb  temperature  of  22°  and  a  wet-bulb 
temperature  of  20°.     The  air  inside  of  a  building  has  a  dry-bulb  temperature 
of  68°.     How  many  gallons  of  water  must  be  used  per  hour  to  raise  the  wet- 
bulb  temperature  of  the  inside  air  to  56°?     The  net  cubic  space  in  the 
building  is  30,000  cubic  feet.     Assume  one  air  renewal  per  hour. 


CHAPTER  XV 
FAN  SYSTEMS  FOR  VARIOUS  TYPES  OF  BUILDINGS 

203.  Types  of  Fan  Systems. — Fan  systems  are  installed 
primarily  to  provide  fresh  air  for  ventilation,  although  in  some 
classes  of  buildings  they  are  preferable  from  a  heating  standpoint 
also.  There  are  various  types  of  fan  systems  and  combinations 
with  direct  radiation,  as  brought  out  in  Chapter  III. 

Perhaps  the  most  common  type  of  system  is  the  so-called  split 
system,  in  which  the  heat  losses  from  the  building  are  supplied  by 
direct  radiation  and  the  fan  system  supplies  air  for  ventilation  at 
nearly  room  temperature.  This  system  is  very  well  adapted 
to  buildings  which  require  ventilation  for  only  part  of  the  time, 
such  as  office  buildings.  The  proper  temperature  can  be  main- 
tained in  the  building  by  means  of  direct  radiation  and  the  fan 
system  need  be  operated  only  when  ventilation  is  required.  In 
such  a  system  the  amount  of  air  supplied  is  determined  entirely 
by  the  ventilating  requirements.  This  type  of  system  is  widely 
used  in  office  buildings,  schools,  manufacturing  establishments, 
etc.  One  objection  to  it  is  its  rather  high  initial  cost. 

In  the  second  type  of  fan  system  some  of  the  heating  is  done  by 
the  fan  system  and  direct  radiation  is  installed  to  take  care  of  the 
balance  of  the  heating  requirements.  The  fan  system  therefore 
delivers  air  at  somewhat  above  room  temperature.  This  system 
is  principally  used  in  schools  and  is  believed  by  many  to  provide 
better  air  distribution  because  the  warm  air  spreads  out  over  the 
room  and  descends  uniformly  as  it  is  gradually  displaced  by  fresh 
warmer  air  above.  It  is  not  feasible  in  most  climates  to  dispense 
with  radiators  in  schools  and  similar  buildings  and  to  supply  all  of 
the  heating  requirements  with  the  fan  system,  for  the  radiators 
are  needed  to  counteract  the  curtain  of  cold  air  descending  in 
front  of  the  windows. 

In  the  third  type  of  system  the  heating  and  ventilating  are  both 
accomplished  by  the  fan  system  and  no  radiation  is  installed. 
This  is  often  called  the  hot  blast  system.  In  such  a  system  the 
amount  of  air  required  may  be  governed  by  either  the  heating  or 
the  ventilating  requirements.  This  system  is  used  in  theatres, 

224 


FAN  SYSTEMS  FOR  BUILDINGS 


225 


226 


HEATING  AND  VENTILATION 


auditoriums,  and  churches.  It  is  most  suitable  for  a  building 
which  must  be  continually  ventilated  during  the  time  of  day  when 
it  is  heated.  In  some  cases  means  can  be  provided  of  recirculat- 
ing  the  air  during  the  warming  up  period  so  as  to  reduce  the  fuel 
consumption. 

The  fourth  type  of  fan  system  has  little  or  no  provision  for 
drawing  in  fresh  air  but  is  used  mainly  for  heating.  Its  use  is 
confined  to  factories  where  the  volume  per  occupant  is  large. 
It  has  some  advantages  over  direct  radiation  in  point  of  first 
cost. 

204.  Office   Buildings. — Office   buildings   are   nearly   always 
heated  entirely  by  direct  radiation  and  when  a  ventilating  system 
is  installed  the  split  system  is  used.     Fig.  153  shows  a  basement 
plan  of  an  office  building  equipped  with  a  system  of  this  type. 
The  air  is  drawn  from  outside  and  passes  through  the  heaters  and 
air  washer  to  the  fan  which  discharges  it  into  a  trunk  duct. 
Branches  and  risers  convey  the  air  to  the  various  rooms  in  the 
building. 

205.  Fan  Systems  for  Schools. — Perhaps  the  most  commonly 
used  system  in  well  built  school  buildings  is  the  second  type  which 


FIG.  154. — Arrangement  of  single  duct  system. 

has  been  described  in  which  the  ventilating  requirements  and 
part  of  the  heating  requirements  are  taken  care  of  by  the  fan 
system.  The  general  arrangement  of  such  a  system  is  shown  in 
Fig.  154. 

The  air  upon  entering  is  passed  through  a  tempering  heater 
which  raises  its  temperature  somewhat  above  the  freezing  point. 
It  then  flows  through  the  air  washer  and  then  in  some  cases 
through  a  reheater  and  then  is  drawn  into  the  fan.  The  fan 
discharges  it  through  an  enlarging  duct  to  the  heating  coils. 
Part  of  the  air  passes  through  the  coils  and  is  heated  to  about 
120°  or  130°,  and  a  portion  passes  below  the  heater  and  enters 
the  tempered  air  chamber  at  a  temperature  of  about  68°.  Each 
duct  leading  to  a  room  is  provided  with  a  double  damper  so 


FAN  SYSTEMS  FOR  BUILDINGS 


227 


arranged  that  air  can  be  taken  partly  from  the  hot  air  chamber 
and  partly  from  the  tempered  air  chamber.  Thermostats, 
located  in  the  rooms  above,  regulate  the  positions  of  these 
dampers  so  that  air  of  the  proper  temperature  to  satisfy  the 
heating  requirements  is  delivered  to  the  respective  rooms.  The 
volume  of  air  remains  nearly  constant.  A  mixing  damper  is 
shown  in  Fig.  155.  The  hot  air  and  tempered  air  chambers  are 
often  jointly  termed  the  plenum  chamber.  They  are  usually 
separated  by  a  double  decking  or  by  an  insulated  partition  to 
prevent  the  transfer  of  heat.  This  type  of  system  is  often  called 


FIG.  155. — Mixing  damper. 

a  single  duct  or  individual  duct  system.     A  basement  plan  of  a 
school  building  having  such  a  system  is  shown  in  Fig.  156. 

School  buildings  are  sometimes  ventilated  by  the  trunk  duct 
or  split  system  similar  to  that  shown  in  Fig.  153.  One  method 
of  distribution  in  a  split  system  is  shown  in  Fig.  157.  The  air  for 
ventilating  is  carried  in  a  trunk  duct  or  plenum  chamber  exca- 
vated below  the  corridor.  Risers  take  air  to  the  various  rooms 
and  the  ducts  are  carried  across  above  the  suspended  ceiling 
and  discharge  the  air  downward  at  several  points,  thus  insur- 
ing even  distribution  throughout  the  room.  Such  a  system  is 
only  practicable  where  the  building  construction  permits  the 
installation  of  the  horizontal  ducts.  The  type  and  arrange- 


228 


HEATING  AND  VENTILATION 


ment  of  the  ventilating  system  is  very  often  considerably 
affected  by  requirements  or  limitations  imposed  by  the  building 
construction. 


The  trunk  duct  system  is  usually  somewhat  less  costly  than  the 
single  duct  system. 


FAN  SYSTEMS  FOR  BUILDINGS 


229 


ff  HI  IL 

I: 

7    r 

Fresh  Air                 ' 
Exhaust 

Ducts                 Di 

\ 

cts 

"E 

tr~   ~TT     IT 

II 

i  : 

*-Wr* 

1; 

)=    ~       PLAN 


/  \   // 


Diffuser 


G.I. 

Sweep 


2nd  Fl. 


Exhaust 


/  /  I  ] 

/    /    u 

Suspended  Ceiling-^ 


1st  Fl.v 


Exhaust- 


ELEVATION 


Attic  Space 
Main  Exhaust  Dust 


Suspended  Ceiling 


Corridor 


Dumpers 


Plenum 
Chamber 


FIG.   157. — Ceiling  distribution  in  a  schoolroom. 


230 


HEATING  AND  VENTILATION 


206.  Exhaust  Ducts. — Provision  must  be  made  for  removing 
the  air  from  the  rooms  at  the  same  rate  at  which  it  is  supplied 


»: 


-V 


IT 


•  ^- 


and  a  system  of  vent  flues  is  provided^for  that  purpose.     The 
flues  from  the  separate  rooms  join  together  in  a  trunk  duct  and 


FAN  SYSTEMS  FOR  BUILDINGS 


231 


Fan  and  Heater 
Located  in  Pent 

House 
Branch  Duct 


lead  to  a  common  discharge  at  the  roof.  The  attic  is  sometimes 
used  as  a  discharge  chamber,  the  flues  leading  directly  to  it. 
Exhaust  flues  are  figured  at  a  velocity  of  600  to  750  feet  per 
minute  and  are  assumed  to  carry  off  the  same  amount  of  air  as  is 
delivered  to  the  room.  In  some  cases  an  exhaust  fan  is  installed 
to  facilitate  the  removal  of  the  foul  air.  The  velocity  in  the 
exhaust  flues  can  then  be  from  1200  to  1500  feet  per  minute.  In 
public  buildings  over  three  or  four  stories  in  height,  where  the 
friction  in  the  exhaust  flues  is  appreciable,  an  exhaust  fan  is 
desirable. 

207.  Factory  Heating. — The   hot-blast   system  is  often  the 
best  system  for  industrial  buildings  as  it  affords  a  means   of 
supplying  fresh  air  to  replace  that   containing  the  fumes  or 
moisture  from  manufacturing  processes.     It  is  also  desirable  in 
factory  buildings  where  the  space  required  by  direct  radiation 
cannot  be  spared.     Owing  to  the  fact  that  such  buildings  are 
seldom  divided  into  many  rooms  the  air 

can  be  supplied  at  a  constant  temperature 
through  a  trunk  system  of  ducts.  A 
draw-through  arrangement  is  almost  uni- 
versally used,  the  heating  coils  being  placed 
on  the  suction  side  of  the  fan,  which  dis- 
charges directly  into  the  main  duct.  For 
ordinary  shop  buildings  of  steel  construc- 
tion, the  ducts  are  of  galvanized  iron  and 
are  suspended  from  the  columns  or  roof 
trusses.  An  example  of  this  arrangement 
is  shown  in  Fig.  158.  In  modern  rein- 
forced-concrete  buildings  the  columns  are 
frequently  made  hollow  and  used  as  the 
air  ducts,  the  heating  apparatus  and  the 
trunk  duct  being  located  on  the  roof  and 
arranged  to  discharge  the  air  into  the  top  Fm.  159.— Hollow  column 

.  T-X-     i  •  method  of  distribution. 

of  each  column.     Discharge  openings  are 

made  in  the  columns  at  each  floor.  The  trunk  duct  and  branch 
ducts  which  are  on  the  roof  must  be  well  insulated.  Details  of 
this  method  of  construction  are  shown  in  Fig.  159.  The  air  is 
sometimes  carried  underground  in  brick  or  concrete  ducts,  but 
the  heat  loss  from  such  ducts  is  considerable. 

208.  Fan  Systems  for  Churches,  Theatres,  and  Auditoriums.— 
Buildings  of  this  class  are  usually  both  heated  and  ventilated 


232 


HEATING  AND  VENTILATION 


by  the  fan  system,  except  that  where  there  are  windows  in  the 
auditorium,  as  in  churches,  it  is  advisable  to  install  direct  radia- 
tors under  them  to  counteract  the  cold  down  draft  which  they 
create.  The  offices,  entrance  lobby,  stage,  etc.  of  such  buildings 
require  direct  radiation.  The  ventilating  requirements  in  such 


BASEMENT  PLAN 


TS"- 


LONGITUDINAL  SECTION 
FIG.   160. — Ventilation  of  auditorium  by  plenum  chamber  method.1 


buildings  are  paramount  and  in  fact  the  problem  is  often  one 

of  cooling  rather  than  heating,  after  the  audience  has  gathered. 

The  air  for  ventilation  may  be  admitted  through  registers 

near  the  stage  and  along  the  sides  of  the  auditorium.     It  is 

1Courtesy  of  SMITH,  HINCHMAN  &  GRYLLS,  Architects  &  Engineers. 


FAN  SYSTEMS  FOR  BUILDINGS 


233 


always  preferable  to  cause  the  air  to  move  toward  the  faces  of 
the  audience  rather  than  to  blow  on  them  from  the  rear.  More 
uniform  distribution  can  usually  be  secured  by  introducing 
the  air  through  a  large  number  of  small  openings  in  the  floor 
beneath  the  seats.  To  accomplish  this  the  space  below  the 
floor  is  used  as  a  plenum  chamber.  Fig.  160  shows  a  fan  system 


FIG.  161.— Unit  ventilator. 

in  a  church  building  arranged  in  this  manner.  This  building 
has  an  exhaust  system  also,  which  draws  the  foul  air  from  the 
upper  part  of  the  auditorium.  A  recirculating  duct  (not  shown) 
conducts  the  exhausted  air  back  to  the  fresh  air  shaft  when 
desired,  so  that  the  warming  up  of  the  building  can  be  accom- 


234  HEATING  AND  VENTILATION 

plished  economically.     No  recirculating  is  done  when  the  audi- 
torium is  occupied. 

The  chief  objection  to  the  plenum  method  of  distribution  is 
the  cost  of  the  plenum  chamber. 

209.  Unit  Ventilation  System. — A  comparatively  recent  devel- 
opment  in   ventilating  systems  is  the  unit  ventilator  system. 
In  this  system  one  or  more  small  fans  and  heaters  are  located 
in  each  room  and  discharge  air  directly  into  the  room.     In 
factory  buildings  they  usually  simply  recirculate  the  air  but 
some  types  are  arranged  to  draw  air  from  outside.     One  of  the 
latter,  sometimes  used  in  schools,  is  shown  in  Fig.  161. 

The  principal  advantage  in  unit  ventilators  is  the  saving  in 
air  duct  work,  which  in  some  instances  is  considerable.  The 
disadvantages  are  the  space  occupied,  their  appearance  and  the 
fact  that  no  air  washer  can  be  installed. 

210.  Methods   of  Estimating  Heating  Requirements. — It  is 
frequently  necessary  to  estimate  the  cost  of  heating  a  building, 
prior  to  its  construction.     It  is  very  difficult  to  do  this  accurately, 
first,  because  of  the  inaccuracies  that  are  inevitable  in  the  com- 
putation of  the  heat  losses,  and  second,  because  of  the  pro- 
nounced effect  of  the  manner  in  which  the  firing  is  done  and 
in  which  the  heating  and  ventilating  system  is  handled. 

The  most  satisfactory  method  is  to  compute  the  theoretical 
heat  loss  and  to  apply  a  factor  to  allow  for  the  manner  in  which 
it  is  believed  the  plant  will  be  handled.  To  compute  the  total 
heat  loss  from  the  building,  it  is  necessary  to  assume  the  tempera- 
ture at  which  the  building  is  to  be  carried  and  the  average  out- 
door temperature.  The  heat  required  for  ventilation  will  depend 
upon  the  amount  of  air  used  and  the  number  of  hours  of  use. 

Example. — Given  a  school  building  heated  with  direct  radiation  and 
equipped  with  a  ventilating  system.  With  the  following  data  furnished, 
what  would  be  the  annual  fuel  cost? 

Heat  loss  from  the  building  per  hour  per  degree  difference  in  temperature 
between  the  inside  and  outside,  12,500  B.t.u.,  not  including  ventilation. 

Average  outside  temperature  for  heating  season,  38°. 

Hours  use  of  building,  8: 00  a.m.  to  4: 00  p.m.,  5  days  per  week. 

Amount  of  air  supplied  for  ventilating,  40,000  cubic  feet  per  minute. 

Cubic  feet  of  space,  300,000. 

The  actual  time  during  which  the  building  is  used  is  8  hours  per  day. 
Let  us  assume  that  a  temperature  of  68°  is  maintained  for  10  houfte  of  each 
of  the  5  school  days  or  50  hours  per  week.  Allowing  for  vacations,  we  may 
assume  that  the  school  is  occupied  for  32  weeks  of  the  heating  season,  or 


FAN  SYSTEMS  FOR  BUILDINGS  235 

1,600  hours  per  year.  For  the  remainder  of  the  8  months  or  5,760  hours  in 
the  heating  season,  the  temperature  may  be  assumed  to  average  50°.  The 
heat  loss,  not  including  ventilation,  would  then  be  as  follows: 

12,500  X  (68  -  38)  X  1,600  =    600,000,000  B.t.u. 
12,500  X  (50  -  38)  X  4,160  =    623,000,000  B.t.u. 

1,223,000,000  B.t.u. 

The  ventilating  fan,  if  properly  handled,  would  be  operated  only  during 
the  actual  hours  of  occupancy  or  40  hours  per  week,  1,280  hours  per  year. 
The  air  handled  by  the  fan  is  heated  from  the  average  outside  temperature 
of  38°  to  the  room  temperature,  68°.  The  heat  loss  from  this  source  would  be 

60  X  40,000  X  1,280  X  0.019(68  -  38)  =  1,750,000,000  B.t.u. 

During  the  remainder  of  the  time,  the  air  may  be  assumed  to  change  1^ 
times  per  hour  due  to  infiltration. 

300,000  X  1.5  X  4,480  X  0.019(50  -  38)  =  460,000,000  B.t.u. 

The  total  heat  loss  is  then,  3,433,000,000  B.t.u. 

Assume  that  the  coal  used  contains  13,000  B.t.u.  and  costs  $6  per  ton. 
For  a  plant  of  this  nature,  operated  by  efficient  help,  we  may  safely  assume 
that  60  per  cent,  of  the  heat  in  the  fuel  is  delivered  to  the  building.  The 
total  annual  cost  would  then  be 

3-433'000-000    X    *--  $1,309 
13,000  X  0.60       2,000 

This  is  the  estimated  cost  on  a  strict  basis.  It  would  be  well  to  add  about 
10  per  cent,  for  safety,  making  the  final  estimate  $1,440.  If  unskilled  help 
were  to  have  been  used  or  if  there  were  other  known  factors  tending  to  ex- 
travagance in  the  use  of  heat,  it  might  be  necessary  to  increase  the  strict 
figure  by  as  much  as  30  per  cent,  in  extreme  cases. 


211.  Heating  Requirements  of  Various  Types  of  Buildings. — 

The  variation  in  the  amount  of  heat  used  in  different  types  of 
buildings  is  shown  in  Table  XL,  which  gives  data  for  a  number 
of  steam-heated  buildings  in  Detroit,  Michigan.  These  build- 
ings are  all  heated  from  a  central  station.  The  heat  loss  per 
hour  per  degree  difference  in  temperature  is  given  for  each 
building.  It  will  be  noticed  that  the  steam  consumption  per 
B.t.u.  of  computed  heat  loss  varies  greatly  for  the  individual 
buildings  and  that  the  average  figures  for  the  different  classes 
of  buildings  are  also  quite  different. 


236 


HEATING  AND  VENTILATION 


TABLE  XL. — STEAM  CONSUMPTION  OF  BUILDINGS  AT  DETROIT,  MICHIGAN 

Heating  Season  of  1914-15 
Average  Temperature  for  Heating  Season  (Oct.  1  to  May  31)— 38.9° 


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273,000 

13,100 

1,860,676 

487 

6,810 

142.0 

4 

5,280 

367,000 

16,700 

3,563,200 

668 

9,700 

213.5 

5 

15,300 

1,350,000 

65,000 

12,632,048 

825 

9,350 

194.2 

6 

7,940 

584,000 

29,100 

4,942,767 

622 

8,460 

169.8 

7 

50,0003 

3,220,000 

120,000 

34,209,387 

684 

10,630 

285.0 

8 

79,500» 

4,900,000 

205,000 

41,850,000 

527 

8,540 

204.2 

Totals  and 

weighted     aver- 

RaETAHY  STORE 

171,119 

11,569,000 

491,500 

104,542,342 

610 

9,020 

212.5 

BUILDINGS 

Building  No. 

1 

1,673 

160,960 

8,715 

627,200 

375 

3,900 

71.9 

2 

1,256 

111,500 

6,400 

364,700 

290 

3,270 

57.0 

3 

16,100» 

2,725,100 

104,000 

7,254,078 

451 

2,660 

69.8 

4 

11,3153 

1,063,100 

42,400 

6,012,348 

531 

5,660 

141.9 

5 

3,864 

403,000 

18,700 

2,110,900 

550 

5,250 

112.9 

6 

2,684 

459,400 

18,400 

987,000 

368 

2,150 

53.6 

7 

4,413 

325,500 

17,700 

1,677,800 

380 

5,140 

94.6 

8 

1,701 

199,000 

8,690 

1,437,600 

843 

7,210 

165.0 

9 

3,632 

613,000 

21,600 

3,133,650 

862 

5,110 

145.0 

10 

2,620 

393,000 

16,500 

1,539,560 

587 

3,910 

93.2 

11 

2,513 

350,000 

11,890 

2,214,200 

880 

6,320 

186.1 

12 

2,162 

197,800 

8,200 

1,072,900 

496 

5,420 

130.8 

Totals  and 

weighted     aver- 

RaESIDENCES:  ' 

53,933 

7,001,360 

283,195 

28,431,936 

527 

4,060 

100.5 

Totals    and    av- 

erages   for    1  14 
buildings  

65,421 

3,156,800 

304,499 

37,484,000 

573 

11,870 

123.0 

GARAGES: 

Totals   and   av- 

erages    for     12 
buildings  

11,414 

1,219,700 

74.243 

9,949,800 

870 

8,160          134.0 

1  B.t.u.  per  hour  per  degree  difference  between  inside  and  outside  temperatures. 

2  Including  steam  for  heating  water. 

3  Including  equivalent  of  fan  coil. 


CHAPTER  XVI 
DESIGN  OF  FAN  SYSTEMS 

212.  Calculation  of  Air  Quantities. — The  first  step  in  the  de- 
sign of  a  fan  system  is  the  calculation  of  the  quantity  of  air  to  be 
handled  and  the  amount  of  heat  which  must  be  imparted  to  it. 
When  ventilation  only  is  considered  the  quantity  of  air  to  be 
handled  by  the  fan  is  governed  by  the  number  of  people  in  the 
building  and  the  amount  of  air  to  be  supplied  per  person.  In 
Chapter  XIV  the  considerations  affecting  ventilation  require- 
ments were  discussed,  and  in  Table  XXXIX,  page  208,  are  given 
the  quantities  required  per  person  or  the  number  of  air  changes 
per  hour  for  various  classes  of  buildings. 

In  the  case  of  a  fan  system  supplying  air  for  ventilation  only, 
as  in  the  split  system  previously  described,  the  heat  which  must 
be  added  to  the  air  is  that  which  is  required  to  raise  its  tempera- 
ture from  the  outside  temperature  (taken  as  the  minimum  to  be 
expected)  to  the  temperature  of  delivery  to  the  room.  If  Q  is 
the  total  quantity  of  air  to  be  introduced  per  hour  and  Hl  is  the 
heat  which  must  be  added  to  the  air  in  B.t.u.  per  hour,  then: 

Hv  =  QD2CP(12  -  h)  (1) 

in  which  Cp  =  specific  heat  of  air  at  constant  pressure  (=  0.2415). 

ti    =  temperature  of  outside  air. 
ti    =  temperature  of  delivery  to  rooms. 
D2  =  density  of  air  at  temperature  £2  in  pounds  per 
cubic  foot. 

In  this  expression  the  heat  absorbed  by  the  water  vapor  is 
neglected  but  the  formula  is  sufficiently  accurate  for  ordinary 
purposes.  If  the  minimum  outside  temperature,  for  which  the 
system  is  to  be  designed,  is  0°  and  the  inside  temperature  is  70°, 
then  D2  =  0.07495  and  formula  (1)  becomes 

Hv  =  Q  X  0.07495  X  0.2415(70  -  0) 

Hi  =  1.27Q  (2) 

In  the  case  of  a  fan  system  supplying  the  heat  which  is  lost 
through  the  wall  and  glass  surface  a  further  amount  of  heat  must 

237 


238  HEATING  AND  VENTILATION 

be  added  to  the  air  delivered.  The  air  after  entering  the  rooms 
is  cooled  to  room  temperature  and  discharged  to  the  outside  at 
that  temperature.  The  total  heat  added  to  the  air  may  there- 
fore be  thought  of  as  being  divided  into  two  parts:  (a)  that 
which  would  be  added  were  ventilation  only  being  considered, 
which  is  the  quantity  required  to  raise  the  air  from  the  outside 
temperature  to  room  temperature,  and  (6)  the  additional  amount 
added  to  supply  the  heat  lost  through  the  walls.  The  latter 
quantity  may  be  expressed  in  the  following  form,  using  the  same 
notation  as  above. 


Hh  =  QD,CP(t,  -  t2)  (3) 

in  which  t3  =  temperature  at  which  the  air  is  delivered. 

Z>2  =  density  at  room  temperature,  pounds  per  cubic 
foot. 

The  air  volume  Q  is  ordinarily  taken  at  room  temperature, 
assumed  to  be  70°. 

Then 

II  =  Hv  +  Hh  =  QD,Cp(t,  -  h)  +  QD,Cp(t,  -  t,)         (4) 

The  quantity  of  air  Q  may  be  governed  either  by  the  venti- 
lating requirements  or  by  the  heating  requirements.  If  the  heat 
loss  from  the  building  is  large,  a  large  quantity  of  air  at  the 
maximum  temperature  to  which  it  is  practicable  to  heat  it,  must 
be  introduced,  and  this  quantity  may  be  greatly  in  excess  of  that 
required  for  ventilation.  On  the  other  hand,  if  the  room  is  to 
contain  a  large  number  of  people  and  if  the  heat  loss  is  compara- 
tively small,  then  the  quantity  of  air  will  be  fixed  by  the  venti- 
lation requirements  and  the  temperature  of  delivery,  £3,  will  be 
fixed  by  the  heating  requirements. 


Example. — Consider  an  auditorium  which  seats  400  people  and  which  is 
to  be  ventilated  with  an  allowance  of  1500  cubic  feet  per  hour  per  person. 
Assume  that  the  fan  system  is  to  supply  the  heat  losses  as  well  as  the  ventila- 
tion requirements,  and  that  a  temperature  of  68°  is  to  be  maintained.  Let 
Hh,  the  heat  loss  through  the  exposed  wall  and  glass  surface  be  860,000 
B.t.u.  per  hour,  and  assume  that  the  air  is  to  be  delivered,  under  maximum 
conditions,  at  a  temperature  of  140°.  From  formula  (3)  Hh  =  QDzCp(ta  —  it) 
and 

Hh 860,000 

W  ~  D2Cp(tz  -  t2)  ~  0.07524  X  0.2415(140-68) 
=  657,000  cubic  feet  per  hour. 


DESIGN  OF  FAN  SYSTEMS  239 

Since  the  amount  of  air  required  for  ventilation  was  set  at  600,000  cubic 
feet  per  hour,  it  is  evident  that  the  amount  introduced  for  heating  require- 
ments will  be  ample  for  ventilation. 

Now,  assume  that  instead  of  400  people,  there  are  500  to  be  provided  for, 
requiring  750,000  cubic  feet  per  hour.  The  657,000  cubic  feet  demanded  by 
the  heating  requirements  will  then  be  insufficient  and  the  quantity  delivered 
must  be  that  required  for  ventilation,  its  temperature,  tZj  being  below  140°. 
The  temperature,  t3,  may  be  computed  from  equation  (3). 

860,000  =  750,000  X  0.07524  X  0.2415(£3  -  68) 
tt  =  131° 

In  some  cases  the*fan  system  is  designed  to  take  care  of  a 
portion  of  the  heat  losses  only,  the  balance  being  supplied  by 
direct  radiation.  The  quantity  Hh  is  then  taken  as  an  arbitrary 
part- — usually  one-third  of  the  computed  heat  loss. 

213.  Flow  of  Air  in  Ducts. — When  air,  like  other  fluids,  is 
moved  through  a  pipe  or  duct,  a  certain  pressure  or  head  is 
necessary  to  start  and  maintain  the  flow.  This  head  has  two 
components.  The  static  head  is  that  which  is  required  to  over- 
come the  frictional  resistance  of  the  air  against  the  surface  of  the 
duct.  The  velocity  head  is  the  pressure  required  to  produce  the 
velocity  of  flow.  The  sum  of  these  two  components  is  termed 
the  total  or  dynamic  head. 

The  static  and  velocity  heads  are  mutually  convertible.  The 
velocity  head  depends  entirely  upon  the  velocity  of  flow  and  if 
the  velocity  in  the  duct  is  decreased  at  any  point  because  of  an 
increase  in  the  cross-sectional  area,  a  portion  of  the  velocity  head 
will  be  converted  into  static  head.  Conversely,  when  the  area 
is  reduced,  the  static  head  is  partially  converted  into  velocity 
head.  The  interchange,  however,  is  always  accompanied  by  a 
certain  amount  of  net  loss  of  head,  depending  upon  the  abrupt- 
ness of  the  change  in  area  and  shape  of  the  section  in  which  the 
change  of  area  takes  place. 

The  velocity  head  may  be  considered  as  the  height  of  a  column 
of  air  which  will  have  at  its  base  a  pressure  sufficient  to  produce 
the  given  velocity,  the  relation  being  represented  by  the  common 
expression,  v2  =  2gh.  To  express  the  velocity  head  in  inches 
of  water,  the  usual  standard,  let 

D  =  density  of  air  under  the  given  conditions,  pounds  per 

cubic  foot. 

Df  =  density  of  water  =  62.3  pounds  per  cubic  foot  at  70°. 
Jiv  =  velocity  head  in  inches  of  water. 
h    =  velocity  head  in  feet  of  air. 


240  HEATING  AND  VENTILATION 

Then 

^-s*     or    *  =  it§ 

V2  =  3600  X  20 


in  which  V  is  the  velocity  in  feet  per  minute. 

V  =  1096.5  -v  (1) 


The  static  head  or  pressure  in  an  air  duct  may  be  thought  of  as 
the  pressure  tending  to  burst  the  duct  and  it  may  therefore  be 
readily  measured  by  means  of  a  water  gage  communicating  with 
the  duct  in  the  manner  shown  at  A  in  Fig.  162.  The  deflection 
of  the  water  levels  will  then  indicate  the  static  pressure  directly 
in  inches  of  water.  The  total  or  dynamic  head  is  measured  by  a 
tube  whose  open  end  points  against  the  flow  as  at  B.  Since  the 
velocity  varies  at  different  points  in  the  cross-section  of  the  duct, 
any  single  reading  of  the  total  pressure  applies  only  to  the  particu- 
lar location  of  the  tube  in  the  duct.  The  velocity  head,  which 
is  equal  to  the  difference  between  the  total  and  static  heads,  can 
be  computed  from  them  or  can  be  measured  directly  by  con- 
necting the  U-tube  as  at  C  in  Fig.  162. 

The  relation  between  the  velocity  and  the  velocity  head 
affords  a  convenient  method  for  measuring  the  flow  of  air  through 
pipes.  For  this  purpose  the  pitot  tube  illustrated  in  Fig.  162a 
is  used  in  practice.  The  tube  is  inserted  into  the  pipe  in  such 
a  manner  that  the  head  A—B  is  parallel  to  the  flow  of  air,  with 
the  end  A  toward  the  flow.  The  part  A—B  consists  of  an  inner 
tube  which  transmits  the  total  pressure  to  the  tube  D  and  an 
outer  jacket  through  which  the  static  pressure  is  transmitted 
to  the  tube  C.  This  outer  jacket  contains  several  small  holes 
through  which  the  static  pressure  is  transmitted.  The  two 
pressures  are  transmitted  to  the  ends  of  the  differential  slant 
gage  E,  which  is  a  U-tube  arranged  with  one  leg  at  an  angle  so 
that  the  linear  deflection  per  inch  of  height  is  increased.  Gages 
of  this  type  are  usually  filled  with  oil  but  are  calibrated  to  read 
in  inches  of  water  column.  The  reading  on  the  gage  is  evidently 
the  velocity  head,  being  the  difference  between  the  static  and 
total  heads. 


DESIGN  OF  FAN  SYSTEMS 


241 


As  has  been  stated,  the  velocity  of  flow  is  not  constant  at  all 
points  in  the  cross-section  of  the  duct.  Near  the  walls  it  is 
retarded  by  friction  and  it  reaches  a  maximum  at  the  center 
of  the  pipe.  It  is  therefore  necessary  to  measure  the  velocity  at 
several  points  in  the  pipe  in  order  to  obtain  an  average  figure. 
In  a  square  or  rectangular  duct  the  cross-section  is  divided  into 


FIG.  162. 


Inclined  Manometer 


FIG.  162a.— Pitot  tube. 

several  equal  rectangles  and  readings  are  taken  with  the  pitot 
tube  at  the  center  of  each  of  these  divisions.  The  velocity  cor- 
responding to  the  pressure  at  the  point  where  each  reading  is 
taken  is  then  computed  from  formula  (1),  p.  240,  in  feet  per 
minute.  The  average  of  these  computed  velocities  is  taken  as 
the  -average  velocity  in  the  pipe.  The  quantity  of  air  flowing 
can  be  readily  computed  from  the  velocity  and  the  cross-sec- 
tional area  of  the  pipe. 

16 


242 


HEATING  AND  VENTILATION 


For  a  round  pipe  the  cross-sectional  area  should  be  divided 
into  a  number  of  annular  zones  of  equal  area  and  a  traverse  of  the 
pipe  should  be  made  in  both  a  vertical  and  a  horizontal  direction, 
as  shown  in  Fig.  163.  For  each  foot  of  pipe  diameter  the  cross- 
section  should  be  divided  into  at  least  three  of  these  zones. 
Table  XLI  gives  the  distance  from  the  center  of  the  pipe  at  which 
each  reading  should  be  taken  in  per  cent,  of  the  pipe  diameter. 


1700 


1800     1900   2000 
Velocity 


FIG.  163. — Division  of  round  pipe  into  annular  zones. 

It  is  important  that  the  velocities  be  computed  separately  and 
averaged,  for  the  velocity  varies  as  the  square  root  of  the  pressure 
and  accurate  results  can  not  be  obtained  by  averaging  the  pressure 
readings.  The  method  outlined  above  is  the  standard  method 
adopted  by  the  American  Society  of  Heating  and  Ventilating 
Engineers.1 


TABLE  XLI. — PIPE  TRAVERSE  FOR  PITOT  TUBE  READINGS 

Distance  from  Center  of  Pipe  to  Point  of  Reading  in  Per  Cent,  of 

Pipe  Diameter 


No.  of 
equal  areas 
in  traverse 

No.  of 
readings 

Istfli 

2d  R2 

3d  R3 

4th  R* 

5th  Rt, 

6th  R& 

7th  #7 

8th  fig 

3 

12 

20.4 

35.3 

45.5 

4 

16 

17.7 

30.5 

39.4 

46.6 

5 

20 

15.5 

27.2 

35.3 

41.7 

47.4 

6 

24 

14.5 

25.0 

32.3 

38.2 

43.3 

47.9 

7 

28 

13.4 

23.1 

29.9 

35.3 

40.1 

44.3 

48.2 

8 

32 

12.5 

21.6 

28.0 

33.2 

37.6 

41.5 

45.1 

48.4 

1  Report  of  Committee  on  Standardization  of  Use  of  Pitot  Tube.     Trans. 
A.  S.  H.  &  V.  E.,  1914. 


DESIGN  OF  FAN  SYSTEMS  243 

214.  The  Anemometer. — For  very  approximate  results,  the 
anemometer,  Fig.  164,  is  a  convenient  instrument  for  measuring 
the  flow  of  air  at  the  duct  outlets.  For  very  low  velocities  it  is 
not  suitable,  as  the  power  required  to  revolve  the  propeller  is  then 
the  source  of  a  considerable  error.  In  using  the  anemometer  the 
face  of  the  register  is  divided  into  a  number  of  equal  areas  and 
the  readings  taken  at  the  several  areas  are  averaged.  The  dial 


FIG.  164  .—Anemometer. 


is  calibrated  to  read  directly  in  feet  and  the  velocity  is  obtained 
by  taking  the  registration  of  the  instrument  during  a  definite 
period  of  time. 

215.  Friction  Loss. — The  general  expression  for  the  friction  of 
fluids  in  pipes  (equation  (3),  page  158)  is  applicable  to  air: 


or  for  round  ducts  of  perimeter  R  and  length  L 

fRL  Dv2  fRL   v2 

Jr  —  -        — —  or  ha  =  - 

a      2g  a      2g 


244 


HEATING  AND  VENTILATION 


in  which     P  =  pressure  required  to  overcome  friction,  pounds 

per  square  foot. 

a  =  cross-sectional  area  of  duct,  square  feet. 
D  =  density  of  air,  pounds  per  cubic  foot. 
v  —  velocity,  feet  per  second. 
/  =  coefficient  of  friction. 
ha  =  height  in  feet  of  a  column  of  air  equivalent  to  P. 


8    1   8     8   o      8    &  S     J9 


v: 


8   S     8  SS     S3  N.     w.   ^."S.0.c~.oc.0i3 
\  Faction  in  Inches  Water  Gage  per  100  Feet 
FIG.  165. — Fractional  resistance  in  round  air  ducts. 


It  is  more  convenient  to  express  the  friction  head  in  terms  of 
inches  of  water.     If  the  density  of  air  at  70°  be  taken  as  0.075 


DESIGN  OF  FAN  SYSTEMS 


245 


and  the  density  of  water  as  62.3  pounds  per  cubic  foot  then  the 
head  in  inches  of  water  is 


k-°^g*»  —  £-  0.00022 

62.3  a     2g  a 


.2 


The  value  of  /  was  found  by  Reitschel  and  others  to  be  about 


TABLE  XLII. — DIAMETER  OF  ROUND  DUCTS  EQUIVALENT  TO  RECTANGULAR 
DUCTS  OF  VARIOUS  DIMENSIONS 


Side 
rectangular 
duct 

4 

6 

8 

10 

12 

14 

15 

16 

18 

20 

22 

24 

Equivalent  diameters 

3 

4 

4.4 

5 

4.9 

6 

5.4 

6.6 

7 

5.8 

7.0 

8 

6.1 

7.6 

8.8 

9 

6.5 

8.0 

9.3 

10 

6.8 

8.4 

9.8 

11.0 

11 

7.1 

8.8 

10.2 

11.5 

12 

7.4 

9.2 

10.7 

12.0 

13.2 

13 

7.6 

9.6 

11.1 

12.5 

13.7 

14 

7.6 

9.9 

11.5 

12.9 

14.3 

15.4 

15 

8.2 

10.2 

11.9 

13.4 

14.7 

16.0 

16.5 

16 

8.4 

10.5 

12.3 

13.8 

15.2 

16.5 

17.1 

17.6 

17 

8.6 

10.8 

12.6 

14.2 

15.7 

17.0 

17.6 

18.2 

18 

8.9 

11.1 

13.0 

14.6 

1ft,  1 

17.4 

18.1 

18.7 

«19.8 

19 

9.1 

11.4 

13.3 

15.0 

16;5 

17.9 

18.6 

19.2 

20.4 

20 

9.3 

11.6 

13.6 

15.4 

17.0 

18.4 

19.0 

19.7 

20.9 

22.0 

22 

9.7 

12.1 

14.2 

16.1 

17.8 

19.2 

19.9 

20.6 

21.9 

23.1 

24.2 

24 

10.0 

12.6 

14.8 

16.8 

18.5 

20.0 

20.8 

21.5 

22.8 

24.0 

25.2 

26.4 

26 

10.4 

13.1 

15.4 

17.3 

19.2 

20.8 

21.6 

22.3 

23.8 

25.1 

26.3 

27.5 

28 

10.8 

13.5 

15.9 

18.0 

19.8 

21.5 

22.4 

23.1 

24.6 

26.0 

27.3 

28.5 

30 

11.0 

13.9 

16.4 

18.5 

20.5 

22.2 

23.1 

23.9 

25.4 

26.8 

28.2 

29.5 

32 

11.3 

14.3 

16.9 

19.1 

21.1 

22.9 

23.8 

24.6 

26.2 

27.7 

29.1 

30.5 

34 

11.6 

14.7 

17.3 

19.6 

21.6 

23.5 

24.4 

26.3 

26.9 

28.5 

30.0 

31.3 

36 

11.9 

15.1 

17.7 

20.1 

22.2 

24.2 

25.1 

26.0 

27.7 

29.3 

30.8 

32.2 

38 

12.2 

15.4 

18.2 

20.6 

22.8 

24.8 

25.8 

26.7 

28.4 

30.0 

31.5 

33.1 

40 

12.5 

15.7 

18.6 

21.1 

23.3 

25.4 

26.4 

27.3 

29.1 

30.8 

32.4 

33.9 

42 

12.7 

16.1 

19.0 

21.6 

23.8 

25.9 

26.9 

27.9 

29.8 

31.4 

33.0 

34.5 

44 

13.0 

16.4 

19.4 

22.0 

24.3 

26.5 

27.5 

28.5 

30.3 

32.1 

33.7 

35.3 

46 

13.3 

16.7 

19.8 

22.4 

24.8 

27.0 

28.1 

29.1 

31.0 

32.8 

34.6 

36.2 

48 

13.5 

17.0 

20.1 

22.8 

25.2 

27.5 

28.6 

29.6 

31.6 

33.4 

35.2 

37.0 

50 

13.7 

17.3 

20.4 

23.2 

25.7 

28.0 

29.2 

30.3 

32.2 

34.1 

35.9 

37.6 

52 

13.9 

17.6 

20.8 

23.6 

26.2 

28.5 

29.6 

30.7 

32.9 

34.7 

36.5 

38.3 

54 

14.1 

17.9 

21.1 

24.0 

26.6 

29.0 

30.1 

31.2 

33.4 

35.3 

37.2 

38.9 

56 

14.3 

18.2 

21.5 

24.4 

27.0 

29.5 

30.6 

31.7 

33.9 

35.9 

37.8 

39.6 

58 

14.6 

18.4 

21.8 

24.7 

27.4 

30.0 

31.1 

32.2 

34.4 

36.4 

38.4 

40.3 

60 

14.7 

18.7 

22.1 

25.1 

27.8 

30.5 

31.6 

32.7 

34.9 

37.1 

39.1 

40.9 

62 

15.0 

19.0 

22.4 

25.5 

28.2 

30.9 

32.1 

33.2 

35.4 

37.7 

39.6 

41.6 

64 

15.1 

19.2 

22.7 

25.9 

28.6 

31.3 

32.6 

33.7 

35.9 

38.2 

40.2 

42.2 

66 

15.3 

19.5 

23.0 

26.2 

29.0 

31.7 

33.0 

34.2 

36.4 

38.7 

40.8 

42.8 

68 

15.5 

19.7 

23.3 

26.5 

29.4 

32.1 

33.4 

34.7 

36.9 

39.2 

41.4 

43.4 

246  HEATING  AND  VENTILATION 

0.0037  for  smooth  iron  ducts.  Prof.  J.  E.  Emswiler1  reports 
values  for  /  ranging  between  0.004  and  0.006  for  velocities  of  800 
feet  per  minute  and  over,  the  coefficient  decreasing  slightly  as  the 
velocity  increases.  For  practical  purposes  a  somewhat  higher 
coefficient  is  used,  giving  larger  duct  sizes.  Allowance  is  thereby 
made  for  roughness  of  the  duct  surfaces  and  for  accidental 
obstructions. 

The  chart  in  Fig.  165,  which  is  published  by  the  American 
Blower  Co.,  gives  the  friction  in  inches  of  water  per  100  feet 
length  of  duct  for  various  quantities  of  air.  The  chart  is  for 
round  ducts;  to  figure  the  friction  in  a  square  or  rectangular  duct, 
it  is  necessary  first  to  obtain  the  diameter  of  the  equivalent 
round  duct,  which  can  be  done  by  means  of  Table  XLII. 

Example. — Find  the  friction  loss  in  a  20-  by  10-inch  duct  67  feet  long, 
carrying  2,000  cubic  feet  of  air  per  minute.  From  Table  XLIT  we  find  that 
the  diameter  of  the  equivalent  round  duct  is  15.4  inches.  From  the  chart 
in  Fig.  165  the  friction  drop  per  100  feet  of  duct  for  the  given  flow  and  for 
a  diameter  of  15.4  inches  is  readily  found  to  be  0.31  inches  of  water.  For 
a  length  of  67  feet  the  drop  would  be  0.3  X  0.67  =  0.201  inches  of  water. 

The  loss  of  pressure  caused  by  various  obstructions,  such  as 
elbows,  branches,  etc.,  is  usually  expressed  as  a  multiple  of  the 
velocity  head.  The  actual  loss,  however,  is  of  course  a  loss  of 
static  head,  since  the  velocity  head  at  all  points  in  a  pipe,  for  a 
given  quantity  of  air  flowing,  depends  entirely  upon  the  cross- 
sectional  area  at  each  point. 

The  center  line  radius  of  elbows  should  be  equal  to  at  least 
1^2  times  the  width  of  the  duct,  as  demonstrated  by  Frank  L. 
Busey,2  who  obtained  the  following  results  for  elbows  of  square 
cross-section : 

Center  line  radius  in  per  Per  cent,  of  velocity 

cent,  of  pipe  width  head  lost 

50  95 

75  34 

100  17 

150  8 

200  7 

Another  method  is  to  add  to  the  actual  length  of  straight  pipe 
a  certain  length  which  will  have  the  same  friction  loss  as  that  due 

1  See  "  Coefficient  of  Friction  of  Air  Flowing  in  Round  Galvanized  Iron 
Ducts,"  by  J.  E.  EMSWILER,  Trans.  A.  S.  H.  &  V.  E.,  1916. 

2  See  "  Loss  of  Pressure  Due  to  Elbows  in  the  Transmission  of  Air  through 
Pipes  or  Ducts,"  by  FRANK  L.  BUSEY,  Trans.  A.  S.  H.  &  V.  E.,  1913. 


DESIGN  OF  FAN  SYSTEMS 


247 


to  the  resistance  in  question.     The  following  table  gives  the  loss 
of  pressure  due  to  various  obstructions. 

TABLE  XLIII. — PRESSURE  Loss  DUE  TO  VARIOUS  OBSTRUCTIONS 


Per  cent,  of 
velocity 
pressure 

Equivalent 
length  of 
straight  pipe 

Round  elbow  (c  1  radius  1/^j  X  width).           .    ... 

8-10 

10  X  width 

SVifl/rD  elbow 

100.0 

Sciuare  tee                            

100.0 

Branch  from  main  duct 
Angle,  15  degrees  (per  cent,  of  v.  p.  in  branch)... 
30  degrees 

10 
20 

45  degrees                         

25 

Abrupt  entrance  to  pipe                              

50-90 

Coned  entrance  to  pipe 

25 

Registers  (free  area  =  duct  area  =  %  total  area 
of  register). 

1.25 

Air  washers: 


Velocity  through  washer, 
feet  per  minute 

400 
500 
600 
700 


Pressure  loss, 
inches  of  water 

0.15 
0.25 
0.35 
0.45 


Example.  —  Given  an  air  duct  of  square  cross-section  carrying  air  at  a 
velocity  of  900  feet  per  minute,  and  at  a  temperature  of  70°.  Find  the  loss 
of  head  due  to  an  elbow  of  diameter  1^  X  width.  From  formula  (2), 


1  QQ6  5  J    X  0.07495  =  0.0505  inches.     The  pressure 
loss  is  0.08  X  0.0505  =  0.004  inches. 

216.  Proportioning  Duct  Systems.  —  It  is  highly  desirable  that 
the  size  of  the  ducts  be  intelligently  selected  and  that  the  pres- 
sure loss  in  the  system  be  computed  as  accurately  as  possible. 
The  principal  reason  for  doing  this  is  to  insure  the  selection  of  a 
fan  of  the  proper  characteristics;  for  in  order  that  the  required 
quantity  of  air  be  delivered  it  is  necessary  that  a  fan  be  selected 
with  working  head  sufficient  to  overcome  the  resistance  of  the 
system.  Furthermore,  the  proper  proportioning  of  the  various 
branches  will  result  in  the  delivery  of  the  proper  air  quantities 
to  the  various  rooms  without  too  great  a  dependence  upon  the 
use  of  the  dampers. 

In  designing  a  duct  system  it  is  necessary  first  to  select  the 
static  resistance  against  which  the  fan  is  to  operate.  Since  the 


248  HEATING  AND  VENTILATION 

power  consumption  depends  upon  the  resistance,  the  cost  of  power 
is  a  consideration  in  air-duct  design.  A  reduction  in  the  power 
required  can  be  obtained  by  increasing  the  duct  sizes;  but  the 
increased  cost  of  the  larger  ducts  and  the  greater  space  required 
are  opposing  factors. 

There  are  two  general  systems  of  air  distribution  and  the 
method  of  choosing  the  duct  sizes  depends  upon  the  type  of 
system.  In  public  buildings,  particularly  in  schools,  the  single- 
duct  system  is  often  used,  in  which  the  air  is  delivered  to  a  plenum 
chamber  by  the  fan  and  separate  ducts  radiate  to  the  various 
rooms.  In  such  a  system  the  duct  having  the  greatest  resistance 
is  first  designed,  which  fixes  the  pressure  to  be  carried  in  the 
plenum  chamber.  The  other  ducts  are  then  so  designed  as  to 
deliver  the  required  quantities  with  the  given  pressure  differential. 

The  longest  duct  is  designed  on  a  basis  of  certain  assumed 
velocities;  Table  XLIV  gives  those  recommended  by  W.  H. 
Carrier: 

TABLE  XLIV. — VELOCITIES  IN  SINGLE-DUCT  SYSTEMS 

Velocity,  feet  per  minute 

Vertical  flues 400-750 

Horizontal  runs 700-1200 

Wall  registers1 200-400 

Floor  registers1 125-175 

In  industrial  buildings  the  trunk  duct  system  is  used,  consist- 
ing of  one  or  more  main  ducts  with  branches  taken  off  at  inter- 
vals. Such  ducts  are  so  proportioned  as  to  give  an  equal  friction 
loss  per  foot  of  length.  The  outlets  are  designed  for  certain 
velocities  depending  upon  the  size  of  the  room  and  upon  the 
distance  through  which  it  is  desired  to  blow  the  air,  the  possi- 
bility of  objectionable  drafts  being  considered.  It  is  customary 
to  assume  an  outlet  velocity  of  from  700  to  1,500  feet  per  minute, 
an  average  figure  being  1,000  feet  per  minute.  Where  the  rooms 
are  small  or  where  the  outlets  are  not  located  well  above  the 
heads  of  the  occupants,  lower  velocities  are  necessary,  i.e.,  300 
to  400  feet  per  minute.  The  branches  from  the  main  duct 
should  be  so  proportioned  as  to  deliver  the  required  air  quanti- 
ties and  it  is  usually  best  to  provide  dampers  on  the  outlets  so 
that  any  inequalities  in  distribution  can  be  adjusted  after  the 
system  is  installed.  It  is  desirable  to  design  all  air  ducts  on  a 

1  Over  gross  area. 


DESIGN  OF  FAN  SYSTEMS 


249 


basis  of  an  air  density  corresponding  to  the  maximum  air  tem- 
perature to  be  expected. 

217.  Correction  for  Temperature. — The  quantities  for  which 
the  duct  sizes  are  computed  are  the  volumes  at  the  actual 
temperature  of  the  air  flowing.  On  the  other  hand,  the  volumes 
fixed  by  the  heating  and  ventilating  requirements  are  on  a  basis 
of  room  temperature,  i.e.,  about  70°.  The  volumes  upon  which 
the  air  ducts  are  designed  must  therefore  be  determined  by  mul- 
tiplying the  volumes  at  70°  by  the  ratio: 

Density  of  air  at  70°' 
Density  of  air  at  duct  temperature 


PT 

^  ; 

TH 

£ 

1 

f4*- 

—  n  —  u 

1 

I-H 

\\ 

I 

EH 

\\ 

1 

\( 

ct 

1 

3t 

•  N-S\          ^N. 

250' 


1GOO  C.E.M. 


FIG.  166. 

These  ratios  are  given  in  Table  XXXVII,  page  203,  in  the  column 
headed  "  Ratio  to  Volume  at  70°F." 

218.  Example  of  Single  Duct  System. — Assume  that  a  single 
duct  system  is  to  be  designed  and  that  the  longest  duct  is 
arranged  as  in  Fig.  166.  The  air  quantity  when  corrected  for  the 
actual  temperature  is  1,600  c.f.m.,  the  temperature  being  120°. 

We  will  figure  the  horizontal  run  on  a  basis  of  1,000  feet  per 
minute  and  a  duct  of  rectangular  section  will  be  used.  The  area 
of  the  horizontal  duct  will  be  1,600  -r- 1,000  =  1.6  square  feet  and 
a  12- by  19-inch  duct  will  be  used.  For  the  riser  a  velocity  of 
600  feet  per  minute  will  be  used  and  the  required  area  is  1,600  -r- 
600  =  2.75  square  feet,  requiring  a  16-  by  24-inch  duct.  From 
Table  XLII  we  find  that  the  diameter  of  a  round  pipe  equivalent 
to  a  12-  by  19-inch  rectangular  duct  is  16.5  inches  and  for  a  16-  by 
24-inch  duct  21.5  inches.  From  the  chart  in  Fig.  165  we  find 
that  a  pipe  of  16.5  inches  diameter  will  transmit  1,600  c.f.m. 


250  HEATING  AND  VENTILATION 

with  a  friction  loss  of  0.14  inch  per  100  feet,  and  the  loss  for 
a  21.5-inch  pipe  is  0.034  inch  per  100  feet.  To  the  actual 
length  of  straight  pipe  we  must  add  the  equivalent  of  the  elbows, 
which  may  be  taken  (see  Table  XLIII)  as  ten  times  the  actual 
width  of  the  duct  measured  on  the  radius  of  the  elbow.  The 
total  friction  drop  due  to  the  straight  pipe  is  then  as  follows: 


(250  +  10)  X    ~  +  (40  +  13.3)  X  =  0.382  inch 


The  resistance  of  the  register  may  be  taken  as  1.25  times  the 
velocity  head  corresponding  to  a  register  velocity  of  300  feet 
per  minute,  upon  which  basis  the  size  of  the  register  will  be 
selected.  The  velocity  head  we  may  compute  by  means  of 
formula  (2),  page  240. 

^X  0.06848  =  0.0051  inch. 

The  loss  through  the  register  is  0.0051  X  1.25  =  0.006  inch. 
The  loss  at  the  entrance  to  the  duct  from  the  plenum  chamber  we 
will  take  as  80  per  cent,  of  the  velocity  head  corresponding  to  the 
velocity  of  1,000  feet  per  minute. 

0.80  X  hv  =  0.80  X  (An^Vx  0.06848  =  0.045  inch 


(QQO     N 
l  pgg  5) 


The  total  resistance  of  the  duct  is  then 

0.382  +  0.006  +  0.045  =  0.433  inch 

and  the  total  pressure  in  the  plenum  chamber  must  be  equal  to 
this  plus  the  velocity  head  corresponding  to  1,000  feet  per  minute 
or  0.433  +  0.062  =  0.495  inch.  The  remaining  ducts  must 
then  be  of  such  a  size  as  to  use  up  this  available  total  pressure  of 
0.501  inch. 

Assume  the  following  data  for  one  of  the  ducts  : 

Quantity  of  air  delivered,  1,150  c.f.m. 

Register  velocity,  300  feet  per  minute. 

Velocity,  throughout  entire  length,      800  feet  per  minute. 

Total  equivalent  length,  including 

resistance  of  elbows,  110  feet 

The  following  quantities  can  be  computed  : 


Resistance  of  register  =     *~n5S       *  0.06848  =  0.0051  inch. 


Loss  at  entrance  to  duct  =  0.80  X  (i  095  5V  X  0.06848  = 


0.029  inch. 


DESIGN  OF  FAN  SYSTEMS 


251 


Velocity  head  at  entrance 


_  /    800    \ 
~  Vl,096.5/ 


X  0.06848  =  0.036  inch. 


Static  head  to  be  used  up  by  friction  =  0.495  -  (0.0051  + 
0.029  +  0.036)  =  0.425  inch. 

The  friction  loss  per  100  feet  of  duct  must  then  be  0.425  -f-  1.10 
=  0.386  inch.  From  the  chart  in  Fig.  165  the  diameter  of  the 
round  pipe  which  will  give  this  friction  loss  for  1,150  c.f.m.  is 
12.0  inches.  This  is  equivalent  (see  Table  XLII)  to  a  rectan- 
gular pipe  10  by  12  inches  or  8  by  15  inches,  either  of  which  could 
be  used.  The  equivalent  length  allowed  for  the. elbows,  which 
must  necessarily  have  been  estimated,  should  be  revised  if  the 
computed  width  of  the  duct  is  greatly  different  from  the  assumed 
width  upon  which  the  equivalent  lengths  were  estimated,  and 
the  calculation  repeated. 


1.800 


1,500 


FIG.   167. 


219.  Trunk-line  System. — In  a  trunk-line  system,  the  pro- 
cedure would  be  as  follows: 

Assume  a  system  laid  out  as  in  Fig.  167,  in  which  the  quanti- 
ties as  given  are  on  a  basis  of  70°.  The  system  will  be  designed 
for  a  temperature  of  135°  and  the  actual  quantities  flowing  in 
the  various  sections  are  as  follows: 

A-B  11,100  X  1.1230  =  12,465  c.f.m. 

B-C  5,800  X  1.1230  =    6,513  c.f.m. 

C-D  1,800X1.1230=    2,021  c.f.m. 

B-E  3,300  X  1.1230  =    3,706  c.f.m. 

E-F  1,500  X  1.1230  =    1,684  c.f.m. 

The  total  head  at  point  A  must  be  equal  to  the  friction  loss 
in  the  trunk  duct  plus  the  velocity  head  at  D,  the  end  of  the 


252  HEATING  AND  VENTILATION 

trunk  duct.  The  method  of  proportioning  by  a  uniform  friction 
loss  leads  to  a  reduction  in  the  velocity  toward  the  end  of  the 
trunk  and  a  consequent  conversion  of  some  of  the  velocity  head 
to  static  head.  The  absolute  values  of  the  velocity  and  static 
heads  at  A  are  not  important,  the  requirement  being  that 
their  sum  be  equal  to  the  friction  loss  plus  the  velocity  head  at 
D.  On  a  basis  of  velocity  of  1,000  feet  per  minute  the  velocity 

head  at  D  will  be  equal  to(t  nnA  ,)  *X  0.06675  =  0.055  inch  on 

*  ijUyo.o/ 

a  basis  of  135°.  The  friction  drop  may  be  fixed  arbitrarily  and 
we  will  choose  it  in  this  case  as  0.20  inch  per  100  feet,  giving  a 
total  pressure  at  point  A  of  0.20  X  2.25  -f  0.055  =  0.505  inch. 
For  a  friction  drop  of  0.20  inch  per  100  feet  the  diameters  of 
sections  A-B,  B-C,  and  C-D,  would  be  respectively  34.0, 
26.0,  and  17  inches.  The  diameter  of  the  outlet  at  D  would  be 
increased  to  19  inches  to  give  the  required  outlet  velocity  of 
1,000  feet  per  minute.  The  branch  pipe  could  be  designed  for 
the  same  pressure  loss  per  unit  length  but  it  is  more  economical 
to  take  advantage  of  the  full  available  head  and  reduce  the  size 
of  the  pipe.  The  static  head  at  B  can  be  found  by  subtracting 
from  the  static  head  at  A  the  loss  in  section  A-B.  Allowing 
for  the  loss  due  to  entrance  in  the  branch  at  B  and  for  the  final 
velocity  head  at  F  the  allowable  friction  loss  in  sections  B-E  and 
E-F  can  be  determined  and  the  size  of  pipe  chosen  accordingly. 
All  outlets  should  be  provided  with  dampers  so  that  the  proper 
delivery  can  be  obtained  by  adjusting  them  after  the  system  is 
installed. 

220.  Power  Required  for  Moving  Air.  —  The  power  required 
for  moving  air  through  a  system  of  ducts  may  be  expressed  as 
follows  : 

Let      p  =  unit  total  pressure,  inches  of  water. 

a  =  cross-sectional  area  of  duct,  square  feet. 
v  =  velocity  of  air,  feet  per  minute. 

Then  the  horsepower  required  is 


12  X  2.3*  xoOO  =  °-°00158  *» 


If  q  is  the  volume  of  air  delivered  per  minute  in  cubic  feet,  then 
q  =  av  and 

Hp.  =  0.000158  pq 


DESIGN  OF  FAN  SYSTEMS 


253 


221.  Theory  of  the  Centrifugal  Fan.— The  centrifugal  fan 
consists  fundamentally  of  a  wheel  having  several  radial  vanes 
revolving  in  a  casing.  Air  enters  near  the  axis  of  the  wheel, 
flows  to  the  circumference  under  the  influence  of  the  centrifugal 
force  produced  by  the  rotation,  and  is  discharged  through  the 
outlet  which  is  located  tangentially  with  respect  to  the  fan  wheel. 
The  pressure  created  in  a  fan  has  two  separate  and  independent 
sources,  (a)  that  due  to  the  centrifugal  force  imparted  to  the 
masses  of  air  enclosed  between  the  vanes,  and  (6)  the  pressure 
due  to  the  linear  velocity  of  the  air  as 
it  leaves  the  tip  of  the  blades.  The 
efficient  conversion  of  the  velocity  head 
into  static  head  depends  upon  the  proper 
design  of  the  fan  housing,  as  will  be 
shown  later. 

Fig.  168  represents  an  elementary  cen- 
trifugal fan.  Consider  a  thin  layer  of 
air  of  thickness  dx  between  two  of  the 
vanes  at  a  distance  x  from  the  axis  and 
having  an  area  of  S.  The  volume 

of  this  layer  of  air  is  then  Sdx,  and  if  its  density  is  D,  then  the 
weight  will  be  SdxD.  Assume  that  the  fan  outlet  is  completely 
closed  and  that  the  wheel  revolves  at  the  rate  of  o>  radians  per 
second.  Then  the  centrifugal  force1 


FIG.   168. 


df 


'xSdx   D 


df 


The  unit  pressure  dp  corresponding  to  df  is  evidently  =  -~  and 

the  equivalent  head 

„  __  dp  __  df 


Then 


dh  = 


2xdx 
~<T 


Let  TI  be  the  radius  at  the  base  of  the  blade  and  r2  the  radius  at 
the  tip.     Then 

Cr2 

*-JL 


1  Centrifugal  force  =  —    —  for  a  mass  m  at  radius  r. 


254  HEATING  AND  VENTILATION 

If  the  entire  column  of  air  between  the  two  blades  from  the  axis 
to  the  radius  r2  be  assumed  to  be  affected,  then  r\  =  0  and 

»«r,» 

~~ 


If  v  is  the  linear  tip  speed  then  v  =  cor2  and 


The  second  source  of  pressure  is  that  equivalent  to  the  velocity  v 
of  the  air  at  the  blade  tips  which  is  equal  to 


The  total  pressure  or  head  developed  under  the  assumed  condi- 
tions would  then  be 

*  +  *'-£ 

9 

The  above  analysis  is  approximate  only  and  is  complicated 
under  actual  conditions  by  the  effect  of  the  various  sources  of 
pressure  loss  and  by  the  fact  that  the  conversion  of  the  velocity 
head  into  static  head  is  only  partial.  The  analysis  serves  to 
show,  however,  the  relation  between  the  pressure  developed  by  a 
centrifugal  fan  and  the  fan  speed.1 

222.  Fan  Blades  and  Housings.  —  Fan  blades  may  be  designed 
in  either  of  three  ways:  radial,  curved  forward  (i.e.,  in  the 
direction  of  rotation)  or  curved  backward.  In  Fig.  169  is  shown 
graphically  the  effect  in  the  resultant  velocity  of  the  air  due  to 
the  different  blade  designs.  The  air  leaving  the  tip  of  the  blade 
has  a  velocity  component  vit  parallel  to  the  blade  and  a  tangential 
component  v%.  If  the  blade  is  curved  forward  the  resultant 
velocity  v  will  be  greater  than  that  in  the  straight-blade  type 
(for  the  same  peripheral  speed)  and  if  curved  backward  the  resul- 
tant velocity  will  be  decreased.  For  a  given  pressure  the  fan 
with  backward  bent  blades  requires  a  higher  rotative  speed 
than  the  other  types  and  is  therefore  in  some  cases  better  adapted 
to  direct  motor  drive. 

The  velocity  head  developed  by  the  fan  wheel  is  considerably 
greater  than  is  required,  while  the  static  head,  which  is  the  force 

1  For  a  complete  discussion  of  the  subject  see  "Heating  and  Ventilating  of 
Buildings,"  by  R.  C.  CARPENTER. 


DESIGN  OF  FAN  SYSTEMS 


255 


necessary  to  move  the  air  against  the  frictional  resistance  of 
the  duct  system,  is  low.  The  velocity  head  is  therefore  partially 
converted  into  static  head  by  designing  the  housing  in  a  suitable 
scroll  shape  so  that  the  velocity  of  the  air  is  gradually  reduced. 
The  efficiency  with  which  the  conversion  to  static  head  takes 
place  depends  upon  the  proper  design  of  the  housing.  It  is  the 
static  head  developed  by  a  fan  which  is  useful  in  overcoming 
duct  resistance  and  before  the  velocity  head  can  become  available 
it  must  be  converted  into  static  head.  Generally  speaking,  the 


Straight  I  Forward  Backward 

FIG.   169. — Effect  of  various  blade  designs. 

fan  which  has  the  greater  static  head  in  proportion  to  velocity 
head  is  the  more  desirable;  although  the  velocity  head  may  be 
further  converted  to  static  head  after  it  leaves  the  fan  if  the 
velocity  is  reduced  by  a  gradual  enlargement  of  the  duct  area. 
223.  Power  Required  by  a  Fan. — It  has  been  shown  that  the 
power  required  for  moving  air  is 

Hv   = MX  144 

12  X  2,31  X  33,000 

in  which  the  pressure  p  is  expressed  in  inches  of  water. 

If  the  pressure  is  expressed  in  terms  of  the  equivalent  column  of 

air  of  height  h,  then 

hDQ 
P'       33,000 

in  which  D  is  the  density  of  the  air  in  pounds  per  cubic  foot. 
In  a  fan  the  actual  head  developed  is  only  a  portion  of  the 

theoretical  head  —  and  is  represented  approximately  by—' 
The  power  required  to  drive  a  fan  is  then 

DQ 


g  33,000 


256  HEATING  AND  VENTILATION 

in  which  c  is  a  factor  which  takes  into  account  the  mechanical 
losses  in  the  fan.  Combining  all  of  the  constant  factors  we  have 

Hp.  =  Kv2QD 

v  being  the  peripheral  velocity,  which  varies  directly  as  the  speed 
of  the  fan.  Since  Q  varies  directly  as  the  speed,  the  power 
required  varies  as  the  cube  of  the  speed. 

224.  Fan  Performance. — From  a  consideration  of  the  fore- 
going, the  following  laws  can  be  stated  as  to  the  performance 
of  centrifugal  fans: 

For  a  given  fan  delivering  air  through  a  given  piping  system — 

1.  The  capacity  varies  directly  as  the  fan  speed. 

2.  The  pressure  varies  as  the  square  of  the  speed. 

3.  The  speed  and  capacity  vary  as  the  square  root  of  the  pressure. 

4.  Horsepower  varies  as  the  cube  of  the  speed  or  capacity. 

5.  Horsepower  varies  as  the  (pressure). ^ 
For  a  constant  pressure — 

6.  The  speed,  horsepower  and  capacity  vary  as  the  square  root 

of  the  absolute  temperature  of  the  air. 
At  constant  capacity  and  speed — 

7.  The  horsepower  and  pressure  vary  inversely  as  the  absolute 

temperature  of  the  air. 

225.  Fan   Efficiency. — The  true  efficiency  of  a  fan  may  be 
defined  as  the  ratio  of  the  work  done  in  moving  the  air  to  the 
energy  input  to  the  fan.     The  total  efficiency,  which  is  the  true 
efficiency,  is  computed  from  the  total  pressure,  while  the  so-called 
static   efficiency  is   computed  from   the  static  pressure.     The 
efficiency  may  then  be  expressed  as  follows: 

0.000157  X  c.f.m.  X  static  pressure  in  inches 


Static  efficiency  = 


hP. 


™  ,   ,    ~  .  0.000157  X  c.f.m.  X  total  pressure  in  inches 

Total  efficiency  =  - 

hp. 

in  which  hp.  represents  the  horsepower  input  to  the  fan,  and  the 
factor  0.000157  is  the  power  required  to  move  1  cubic  foot  of 
air  per  minute  against  a  pressure  of  1  inch  of  water. 

226.  Straight-blade  and  Multi-blade  Fans. — Centrifugal  fans 
are  of  two  general  types.  The  older  type,  the " steel-plate"  fans, 
has  a  relatively  small  number  of  radial  blades  which  are  nearly 
plane  surfaces.  The  more  recently  developed  "multi-blade"  type 
has  a  large  number  of  short,  curved  blades  on  a  wheel  of  com- 
paratively small  diameter.  In  the  multi-blade  type  the  blades 


DESIGN  OF  FAN  SYSTEMS 


257 


are  usually  curved  forward  as  in  Fig.  169,  so  that  the  pressure 
developed  will  be  greater  than  that  corresponding  to  the 
peripheral  velocity. 

The  two  types  of  fans  have  inherently  different  characteristics. 
In  a  straight-blade  fan  operated  at  constant  speed  the  total  pres- 
sure developed  decreases  as  the  output  of  the  fan  is  allowed  to 
increase  by  reason  of  a  lessened  resistance.  The  multi-blade  fan 
usually  is  designed  to  develop  an  increasing  total  pressure  as  its 
output  is  increased  under  the  same  conditions.  In  Fig.  170  are 
shown  the  pressure  characteristics  of  the  two  types.  The  ver- 


.140 


ogl20 

S.3 
H. 2-100 


80 


40 


'Pressure  Characteristic  of 
Straight  Blade  Fans 


Fon 


•essure  Characteristic_of 
rward  Curved  Blad 


Fans 


20 


60  80  100 

Per  Cent  of  Rated  Capacity 


120 


140 


FIG.   170. — Pressure  characteristics  of  straight-blade  and  multi-blade  fans  at 

constant  speed.1 

tical  ordinate  is  in  terms  of  the  ratio  of  the  total  pressure  to  the 
pressure  corresponding  to  the  peripheral  velocity,  this  standard 
being  used  simply  to  make  the  curves  comparable.  The  prac- 
tical significance  of  these  differing  characteristics  is  evident  when 
the  action  of  a  fan  supplying  a  system  of  ducts  is  considered. 
With  a  straight-blade  fan  if  one  part  of  the  duct  system  were  shut 
off  and  the  fan  speed  is  unchanged  the  result  would  be  an  increase 
in  the  amount  of  air  delivered  to  the  other  rooms.  With  a  multi- 
blade  fan,  on  the  other  hand,  the  quantity  delivered  through  the 

iFrom    The  Centrifugal  Fan,  by  FRANK  L.  BUSEY,  Trans.  A.  S.  H.  & 
V.  E.,  1915. 

17 


258  HEATING  AND  VENTILATION 

remaining  ducts  would  not  be  greatly  altered.  In  ventilating 
work  this  feature  is  usually  desirable,  although  under  many  other 
conditions  the  drooping  characteristic  of  the  straight  blade  fan 
(which  may  also  be  secured  in  certain  types  of  multiblade  fan) 
is  more  suitable.  Other  advantages  of  fans  of  the  multi-blade 
type  are  the  smaller  space  occupied  and  the  fact  that  their 
higher  speed  makes  it  possible  to  connect  them  direct  to  motors. 
The  higher  speed  also  reduces  the  cost  of  the  motor  in  some  cases. 
In  general  the  multi-blade  type  is  the  more  suitable  for  ventilating 
systems. 

In  Fig.  171  are  shown  the  wheels  of  a  straight-blade  and  of  a 
multi-blade  fan  and  in  Fig.  172  is  shown  the  casing  of  a  multi- 
blade  fan.  The  general  appearance  of  the  casings  of  the  two 


FIG.   171. — Wheel  of  straight-blade  fan.     Wheel  of  multi-blade  fan. 

types  is  quite  similar,  the  multi-blade  fan  being  somewhat  smaller 
in  diameter  and  of  greater  width  for  the  same  capacity.  Fans 
can  be  obtained  with  the  discharge  opening  at  various  angles  and 
with  the  inlet  opening  on  either  side.  In  some  cases  fans  of 
double  width,  having  an  inlet  on  both  sides,  are  used. 

227.  Selection  of  a  Fan. — Before  selecting  a  fan  for  a  given 
installation  it  is  necessary  to  know  the  quantity  of  air  to  be 
handled  and  the  static  resistance  of  the  duct  system.  The  total 
pressure  against  which  the  fan  must  operate  is  the  sum  of  the 
static  resistances  on  both  the  suction  and  the  discharge  sides 
of  the  fan  plus  the  velocity  head  at  the  fan  outlet,  which  can  be 
determined  from  the  volume  of  air  delivered  and  the  size  of  the 
outlet.  The  size  of  fan  which  will  fill  the  requirements  is 
best  obtained  from  the  data  published  by  the  various  fan  manu- 
facturers. It  is  usually  possible  to  obtain  the  same  capacity 

17 


DESIGN  OF  FAN  SYSTEMS  259 

and  static  head  from  two  or  more  different  size  fans.  Frequently 
the  fan  which  operates  the  most  efficiently  under  the  given  con- 
ditions is  not  the  lowest  in  first  cost  and  the  selection  must  be 
governed  by  the  relative  importance  of  these  factors. 


FIG.   172. — Casing  of  multi-blade  fan. 

228.  Fan  Tables. — The  exact  performance  to  be  expected  of  a 
fan  under  any  given  conditions  can  be  obtained  from  the  tables 
published  by  the  manufacturers.  There  are  two  kinds  of  fan 
tables — the  total  pressure  tables,  which  give  the  speed, 
capacity,  and  horsepower  for  the  various  size  fans  at  the  most 
efficient  point  for  various  total  pressures ;  and  the  more  complete 
static  pressure  tables,  which  give  the  performance  at  points 
on  either  side  of  the  most  efficient  point.  Tables  XLV  and 
XL VI  are,  respectively,  the  total  pressure  table  for  various  sizes 
of  one  type  of  multi-blade  fan,  and  the  static  pressure  table  for  a 
multi-blade  fan  of  one  particular  size,  the  latter  being  in  a  some- 
what condensed  form.  More  complete  static  pressure  tables  for 
both  steel  plate  and  multi-blade  fans  may  be  found  in  the 
Appendix.  The  static  pressure  tables  are  the  better  adapted  for 
general  use.  The  total  pressure  can  be  found  for  any  conditions 
by  adding  to  the  static  pressure  the  velocity  pressure  as  given  in 
the  third  column  in  Table  XL VI. 


260 


HEATING  AND  VENTILATION 


TABLE  XLV. — CAPACITIES  OF  BUFFALO  NIAGARA  CONOIDAL  FANS  (TYPE  N) 
UNDER  AVERAGE  WORKING  CONDITIONS — AT  70°F. 
AND  29.92  INCHES 


Fan  No. 

Mean 
diam.  of 
blast  wheel 

Area  of 
•   outlet, 
square  feet 

•Hj-in.  total  press, 
or  0.217  oz. 

K-in.  total  press, 
or  0.288  oz. 

R.p.m. 

Vol. 

Hp. 

R.p.m. 

Vol. 

Hp. 

3 

U$i 

1.31 

413 

1,490 

0.13 

478 

1,720 

0.19 

SH 

I8H 

1.79 

354 

2,030 

0.17 

409 

2,350 

0.26 

4 

20^ 

2.33 

310 

2,650 

0.22 

358 

3,070 

0.34 

4}g 

23  H 

2.95 

276 

3,360 

0.28 

318 

3,880 

0.43 

5 

26  H 

3.64 

248 

4,150 

0.35 

287 

4,790 

0.53 

5H 

28  H 

4.41 

225 

5,020 

0.42 

260 

5,800 

0.65 

6 

31H 

5.25 

207 

5,970 

0.50 

239 

6,900 

0.77 

7 

36  H 

7.14 

177 

8,130 

0.68 

205 

9,400 

1.05 

8 

42 

9.33 

155 

10,610 

0.89 

179 

12,260 

1.37 

9' 

47 

11.81 

138 

13,450 

1.12 

159 

15,520 

1.73 

10 

52 

14.58 

124 

16,580 

1.39 

143 

19,160 

2.14 

11 

58 

17.64 

113 

20,070 

1.68 

130 

23,180 

2.58 

12 

63 

21.00 

104 

23,880 

2.00 

119 

27,590 

3.08 

13 

68 

24.65 

95 

28,040 

2.35 

110 

32,370 

3.61 

14 

73 

28.68 

89 

32,520 

2.72 

102 

37,550 

4.19 

15 

78 

32.80 

83 

37,330 

3.13 

96 

43,100 

4.80 

Static  pressure  is  77^  per  cent,  of  total  press. 

TABLE  XLV. — (Continued) 


Fan  No. 

Mean 
diam.   of 
blast  wheel 

Area  of 
outlet, 
square  feet 

£fj-in.  total  press, 
or  0.360  oz. 

j^i-in.  total  press, 
or  0.433  oz. 

R.p.m. 

Vol. 

Hp. 

R.p.m. 

Vol. 

Hp. 

3 

15# 

1.31 

533 

1,930 

0.27 

585 

2,110 

0.35 

3>lj 

18H 

1.79 

457 

2,620 

0.37 

501 

2,870 

0.48 

4 

20  H 

2.33 

400 

3,430 

0.48 

439 

3,750 

0.63 

«u 

23  H 

2.95 

356 

4,340 

0.60 

390 

4,750 

0.80 

5 

26  H 

3.64 

320 

5,350 

0.74 

351 

5,870 

0.98 

5X 

28H 

4.41 

291 

6,470 

0.90 

319 

7,100 

1.19 

6 

31  H 

5.25 

267 

7,710 

1.07 

292 

8,450 

1.41 

7 

36  H 

7.14 

229 

10,490 

1.46 

251 

11,500 

1.92 

8 

42 

9.33 

200 

13,700 

1.91 

219 

15,020 

2.51 

9 

47 

11.81 

178 

17,340 

2.41 

195 

19,000 

3.18 

10 

52 

14.58 

160 

21,400 

2.98 

175 

23,460 

3.93 

11 

58 

17.64 

146 

25,900 

3.60 

160 

28,390 

4.75 

12 

63 

21.00 

133 

30,820 

4.29 

146 

33,780 

5.65 

13 

68 

24.65 

123 

36,180 

5.03 

135 

39,650 

6.63 

14 

73 

28.68 

114 

41,950 

5.84 

125 

45,990 

7.69 

15 

78 

32.80 

107 

48,160 

6.70 

117 

52,790 

8.83 

Static  pressure  is  77>^  per  cent,  of  total  press. 

1  From  "Fan  Engineering,"  Buffalo  Forge  Co. 


DESIGN  OF  FAN  SYSTEMS 


261 


TABLE  XLVL — No.  10  NIAGARA  CONOIDAL  FAN  (TYPE  N) 
Capacities  and  Static  Pressures  at  70°F.  and  29.92  Inches  Barom.1 


Outlet 
velocity, 
ft.-min. 

Capac- 
ity, cu. 
ft.,  air 
per 
mm. 

Add 
for 
total 
press. 

}£-in.  s.p. 

%-in.  s.p. 

1-in.  s.p. 

l^i-in.  s.p. 

2-in.  s.p. 

R.p.m. 

Hp. 

R.p.m. 

Hp. 

R.p.m. 

Hp. 

R.p.m. 

Hp. 

R.p.m. 

Hp. 

1,400 

20,410 

0.122 

164 

2.92 

206 

4.61 

243 

6.59 

308 

11.1 

1,500 

21,870 

0.141 

163 

3.13 

204' 

4.78 

240 

6.83 

305 

11.5 

1,600 

23,330 

0.160 

164 

3.42 

202 

5.02 

238 

7.05 

302 

11.8 

357 

17.0 

1,700 

24,790 

0.180 

165 

3.74 

201 

5.30 

235 

7.28 

299 

12.1 

353 

17.5 

1,800 

26,240 

0.202 

166 

4.13 

200 

5.61 

233 

7.59 

295 

12.4 

350 

17.9 

1,900 

27,700 

0.225 

168 

4.55 

200 

6.01 

232 

7.91 

293 

12.7 

347 

18.3 

2,000 

29,160 

0.250 

171 

5.04 

200 

6.48 

231 

8.32 

291 

13.0 

343 

18.7 

2,100 

30,620 

0.275 

174 

5.56 

201 

7.00 

231 

8.77 

288 

13.5 

340 

19.2 

2,200 

32,080 

0.302 

177 

6.12 

203 

7.54 

230 

9.31 

286 

13.9 

338 

19.6 

2,300 

33,540 

0.330 

180 

6.76 

205 

8.16 

231 

9.92 

285 

14.4 

336 

20.1 

2,400 

34,990 

0.360 

183 

7.43 

207 

8.86 

232 

10.60 

284 

15.0 

332 

20.6 

2,600 

37,910 

0.422 

190 

8.95 

213 

10.40 

235 

12.10 

282 

16.3 

329 

21.8 

2,800 

40,830 

0.489 

198 

10.70 

219 

12.20 

240 

13.90 

283 

18.1 

327 

23.3 

3,000 

43,740 

0.560 

206 

12.70 

226 

14.30 

246 

16.00 

285 

20.1 

326 

25.0 

3,200 

46,660 

0.638 

215 

14.80 

234 

16.70 

251 

18.30 

288 

22.4 

327 

27.4 

NOTE. — Bold-face  figures  indicate  point  of  highest  static  efficiency. 


The  fan  tables  are  based  on  actual  tests  made  by  operating  the 
fan  at  constant  speed  against  different  artificial  resistances  con- 
sisting of  plates,  having  openings  of  various  sizes,  placed  at 
the  end  of  a  straight  pipe  about  30  diameters  in  length.  In 
Fig.  173  are  shown  the  performance  curves  for  a  multi-blade 
fan,  based  on  the  percentage  of  rated  capacity,  the  latter  being 
taken  as  the  point  at  which  the  fan  operates  with  the  highest 
total  efficiency.  It  should  be  borne  in  mind  that  these  perform- 
ance curves  are  based  on  a  constant  speed. 

It  is  frequently  necessary  to  find  the  performance  of  a  fan 
at  some  pressure  different  from  any  given  in  the  tables.  The 
method  of  doing  this  can  best  be  shown  by  a  typical  example. 
Assume  that  38,000  cubic  feet  of  air  per  minute  is  to  be  delivered 
by  a  No.  10  Conoidal  fan  against  a  static  resistance  of  1J£ 
inches.  Find  the  required  speed  and  horsepower.  The  data  for 
1-inch  static  is  given  in  Table  XLVL  The  corresponding  capac- 
ity of  the  fan  at  1-inch  static  may  be  found  by  multiplying  by 
the  square  root  of  the  ratio  of  1-inch  to  IJ^-inch,  since  we  know 
that  the  pressure  varies  as  the  square  of  the  speed  and  conse- 
quently as  the  square  of  the  volume  delivered.  The  capacity  on 


The  Centrifugal  Fan,  by  FRANK  L.  BUSEY,  Trans.  A.  S.  H.  & 
V.  E.,  1915. 


262 


HEATING  AND  VENTILATION 


a  1-inch  basis  is  thus  found  to  be  34,100  c.f.m.  From  Table 
XL VI  we  find  that  the  speed  and  horsepower  for  33,540  c.f.m. 
at  1-inch  static  are  respectively  231  r.p.m.  and  9.92  horsepower. 
The  speed  and  horsepower  at  1^4  inches  static  we  can  compute 
from  our  knowledge  that  the  speed  varies  directly  as  the  capacity 
and  the  power  as  the  cube  of  the  capacity.  The  fan  will  deliver 
38,000  c.f.m.  against  \Y±  inches  static  with  a  speed  of  258  r.p.m. 
and  a  power  consumption  of  13.9  horsepower. 


20 


40 


140 


60  80  100 

Per  Cent  of  Bated  Capacity 

FIG.  173.  —  Performance  curves  of  Niagara  conoidal  fans. 


160 


In  selecting  a  fan  for  a  given  installation  it  is  usually  possible  to 
fulfill  the  required  conditions  with  two  or  even  three  different  sizes 
of  fans.  In  such  a  case  the  first  cost,  operating  cost,  and  out- 
let velocities  should  be  considered  in  making  the  selection.  The 
smaller  the  fan  the  greater  will  be  the  outlet  velocity  for  the 
same  volume.  In  the  case  of  schools  or  other  buildings  where 
quiet  operation  is  essential  the  outlet  velocity  should  not  be 
over  about  2^200  feet  per  minute.  In  industrial  buildings,  how- 
ever, outlet  velocities  of  about  3,000  feet  per  minute  are  quite 
permissible. 

229.  Correction  for  Temperature. — The  fan  tables  are  based 
on  an  air  density  corresponding  to  a  temperature  of  70°.  In 
a  system  in  which  the  fan  is  so  located  with  respect  to  the  heating 
coils  that  it  handles  air  at  a  different  temperature,  a  correction 


DESIGN  OF  FAN  SYSTEMS  263 

must  be  made.     This  can  be  done  by  making  use  of  the  relations 
stated  in  Par.  224. 

For  example:  Assume  that  it  is  required  to  handle  11,700  c.f.m. 
against  a  static  head  of  1%  inches  at  140°.  As  brought  out  in 
Par.  224,  at  constant  capacity  and  speed,  the  horsepower  and 
pressure  vary  inversely  as  the  absolute  temperature  of  the  air. 
Therefore,  if  we  select  a  fan  which  will  handle  11,700  c.f.m. 

against  a  pressure  of  1.75  X  ^7:   =   1.98  inches  at  70 


deliver  the  same  quantity  against  a  pressure  of  1.75  inches  at  140° 
at  the  same  speed.  From  the  fan  tables  we  find  that  a  No.  90 
steel  plate  fan  will  do  this  at  a  speed  of  403  r.p.m.  and  a  power 
consumption  of  7.32  horsepower.  The  power  consumption  at 

530 
140°  would  be  7.32  X          =  6.46  horsepower. 


It  should  be  remembered  that  the  volume  of  air  fixed  by  the 
heating  or  ventilating  requirements  is  usually  based  on  the  room 
temperature  and  the  equivalent  volume  of  the  same  weight  of 
air  at  the  temperature  at  which  it  enters  the  fan  must  be  found 
by  means  of  the  volume  ratios  given  in  Table  XXXVII,  page  203. 

230.  Disc  Fans.  —  The  disc  fan  as  illustrated  in  Fig.  174  is  well 
adapted   for  handling  considerable 

quantities  of  air  against  very  low 
pressures.  It  is  therefore  widely 
used  where  the  air  is  moved  into  or 
from  a  room  without  passing 
through  a  system  of  ducts.  While 
not  highly  efficient,  this  type  of 
fan  is  easily  installed,  is  of  mod- 
erate cost,  and  requires  little  space. 
Such  a  fan  is  usually  inserted  di- 
rectly into  a  wall  or  partition  and  is 
driven  by  a  direct-connected  motor. 

231.  Heaters.  —  In  a  fan  system  the  heat  is  transmitted  from 
the  heating  units  entirely  by  convection,  the  air  being  drawn  over 
them    at    a    fairly    high    velocity.     There    are    two    types    of 
heater    used    for    such    work  —  the    cast-iron    heater    and    the 
wrought-iron  pipe  coil.     The  former  is  made  up  of  sections,  as 
shown  in  Fig.  175,  connected  together  at  the  top  and  bottom  by 
right-  and  left-hand  nipples  cast  with  a  hexagonal  nut  at  the 
middle.     A  row  of  sections  thus  connected  constitutes  a  stack. 


264 


HEATING  AND  VENTILATION 


The  sections  are  obtainable  in  nominal  lengths  of  30,  40,  50,  60, 
and  72  inches.  All  sizes  are  connected  at  both  top  and  bottom 
and  are  therefore  suitable  for  hot  water  as  well  as  steam. 

The  sections  are  furnished  in  two 
widths,  the  " regular"  and  the  "nar- 
row," and  by  the  use  of  nipples  of 
different  lengths  the  distance  between 
sections  can  be  made  either  4^,  5,  or 
5%  inches  center  to  center,  the 
5-inch  spacing  being  standard.  The 
surfaces  are  broken  up  by  a  large 
number  of  projections  which  extend 
into  the  air  passages  and  serve  to 
augment  the  heating  surface  in  an 
effective  manner.  The  principal 
dimensions  of  the  sections  of  various 
sizes  are  given  in  Table  XL VII. 

The  method  of  installing  the  stacks 
in  a  sheet-metal  casing  is  shown  in 
Fig.  176.  The  stacks  are  staggered 
so  as  to  break  up  the  stream  lines 
and  increase  the  intimacy  of  the  contact  between  the  air  and 
the  heating  surface.  The  spaces  left  at  the  ends  of  the  stacks 
due  to  the  staggered  arrangement  are  partially  closed  by  strips 
of  angle  iron. 

TABLE  XLVII. — DIMENSIONS  OF  VENTO  SECTIONS,  INCHES 


FIG.  175. — Cast  iron  heater. 


Nominal  size 

Square  feet 
of  surface 

Actual  height 

Width 

30 

8.00 

30 

9H 

40 

10.75 

41^4 

9M 

Regular  width 

50 

13.50 

50%  2 

9M 

60 

16.00 

601^6 

9>6 

72 

19.00 

72%  2 

9M 

40 

7.50 

41^4 

6^ 

Narrow 

50 

9.50 

502%  2 

SH 

60 

11.00 

60% 

Wi 

Approximate  weight  8.2  pounds  per  square  foot  of  surface. 

232.  Pipe-coil  Heaters. — Heaters  made  of  1-inch  pipes  are 
also  widely  used.  The  pipe  is  made  into  loops  with  ordinary 
elbows,  and  the  loops  are  screwed  into  a  cast-iron  base.  The 


DESIGN  OF  FAN  SYSTEMS 


265 


base  is  so  partitioned  that  the  steam  flows  in  at  one  end  of  each 
of  the  loops.     The  sections  are  arranged  as  shown  in  Fig.  177, 


FIG.  176. — Vento  heater  installed  in  casing. 


P~©~  O  O  O^O  O  O  «P 

r©  © 
ID 

lL  - 


L  -Q-  -@_  QJOL  -©_  fl  L@_  O.  j 


©©©©©©©© 

.O-O-O.Q.Q-fl  &» 


FIG.  177. — Pipe  coil  heater. 

the  pipes  being  staggered  with  reference  to  the  flow  of  air  through 
the  heater.     The  sections  are  built  in  different  sizes  and  a  wide 


266 


HEATING  AND  VENTILATION 


range  in  heating  surface  is  available.  The  complete  heater  is 
composed  of  several  units  in  series,  as  in  the  case  of  the  cast- 
iron  heaters. 

233.  Transmission  of  Heat  from  Fan-coil  Surfaces. — The 
heating  units  are  arranged  in  series,  the  outside  air  entering 
the  first  section  and  being  heated  up  to  the  required  delivery 
temperature  during  its  passage  through  the  successive  sections. 
Since  the  rate  of  heat  transmission  varies  nearly  as  the  tem- 
perature difference  between  the  steam  and  the  air,  the  heat 
transmitted  from  the  last  stacks  is  much  less  than  from  those 
with  which  the  cold  air  first  comes  into  contact. 

The  final  temperature  to  which  the  air  is  heated  depends  upon 
the  number  of  stacks  through  which  the  air  passes  in  series 
and  upon  the  velocity  of  the  air.  The  cross-sectional  area  of  the 
heater  depends  upon  the  quantity  of  air  delivered,  the  stacks 
being  chosen  of  sufficient  size  so  that  the  free  area  between  the 
sections  will  allow  that  quantity  to  pass  through  at  the  velocity 
chosen.  The  free  area  per  section  for  Vento  heaters  is  given  in 
Table  XL VIII.  Similar  data  is  published  by  the  manufacturers 
of  pipe-coil  heaters. 


TABLE  XLVIII. — FREE  AREAS  OP  VENTO  SECTIONS 


Size  ^of  section, 
inches 

Free  area,  square  inches  per  section 

5£fj-in.  centers 

6-inch  centers 

4^-inch  centers 

30 

0.542 

0.460 

0.390 

40 

0.729 

0.620 

0.525 

50 

0.905 

0.768 

0.650 

60 

1.085 

0.921 

0.781 

72 

1.303 

1.104 

0.937 

The  velocity  to  be  assumed  depends  upon  the  nature  of  the 
installation.  In  public  buildings  and  in  other  places  where 
the  noise  which  accompanies  high  velocities  is  objectionable,  the 
velocity  through  the  heater  should  be  limited  to  between  1,000 
to  1,300  feet  per  minute  while  in  factories  and  similar  buildings  a 
velocity  between  1,200  and  1,600  feet  per  minute  is  permissible. 
For  this  purpose  velocities  are  based  on  an  air  density  correspond- 
ing to  70°,  this  being  merely  an  arbitrary  standard  adopted  for 
convenience  in  making  computations.  In  very  cold  climate's  a 


DESIGN  OF  FAN  SYSTEMS 


267 


TABLE  XLIX. — FINAL  TEMPERATURES  AND  CONDENSATION 

Regular  Section — Standard  Spacing,   5-inch  Centers  of  Sections — Steam, 

227°,  5  Pounds  Gage 


a 

vw 

Velocity  through  heater  in  feet  per  minute  —  measured  at  70° 

| 

«.a 

600 

800 

1,000 

1,200 

1,400 

1,600 

1,800 

2,000 

«i 

fc 

Final 

Cond. 

fe-o 

&!* 

tCfIau: 

Ib.  per 

. 

. 

s 

Si3 

leav- 

sq. ft. 

fr 

d 

£ 

0 

S 

o 

£ 

0 

fr 

U 

p-i 

O 

fe 

^ 

3 
fc 

H 

ing 
heater 

per 
hour 

-20 

-10 

34 

1.69 

1 

0 

43 

1.65 

38 

1.95 

35 

2.24 

32 

2.46 

20 

58 

1.46 

54 

1.75 

51 

1.99 

49 

2.23 

47 

2.42 

45 

2.56 

43 

2.65 

42 

2.82 

30 

66 

1.39 

62 

1.64 

60 

1.92 

58 

2.17 

56 

2.33 

54 

2.46 

52 

2.54 

51 

2.69 

-20 

63 

1.60 

55  1.92 

49 

2.22 

44 

2.46 

40 

2.69 

37 

2.92 

34 

3.12 

31 

3.27 

-10 

69 

1.52 

62  1.85 

56 

2.12 

51 

2.35 

47 

2.56 

44 

2.77 

41 

2.94 

38 

3.08 

2 

0 

75 

1.44 

681.74 

62 

1.99 

582.23 

54 

2.42 

51 

2.62 

48 

2.77 

462.95 

20 

87 

1.29 

81 

.57 

76 

1.80 

72  2.00 

69 

2.20 

66 

2.36 

64 

2.54 

622.69 

30 

93 

1.21 

87 

.46 

83 

1.70 

79 

1.89 

76 

2.06 

73 

2.21 

71 

2.37 

69  2.50 

-20 

91 

1.42 

82 

.74 

75 

2.03 

69 

2.28 

64 

2.51 

59 

2.70 

55 

2.88 

52 

3.08 

-10 

96 

1.36 

87 

.66 

80 

1.92 

75 

2.18 

70 

2.39 

66 

2.60 

62 

2.77 

58 

2.90 

3 

0 

101 

1.30 

93 

.59 

86 

1.84 

81 

2.08 

76 

2.27 

72 

2.46 

68 

2.62 

65 

2.78 

20 

110 

1.15 

103 

.42 

97 

1.65 

92 

1.85 

88 

2.06 

85 

2.22 

82 

2.38 

79 

2.52 

' 

30 

115 

1.09 

108 

.33 

103 

1.56 

98 

1.75 

94 

1.91 

91 

2.08 

88 

2.23 

85 

2.35 

-20 

114 

1.29 

103 

.58 

96 

1.86 

90 

2.12 

84 

2.34 

78 

2.51 

74 

2.71 

70 

2.88 

-10 

117 

1.22 

108 

.51 

101 

1.78 

95 

2.02 

89 

2.22 

84 

2.41 

80 

2.60 

76 

2.76 

4 

0 

121 

1.16 

113 

.45 

106 

1.70 

100 

1.92 

95 

2.13 

90 

2.31 

86 

2.48 

82 

2.63 

20 

130 

1.06 

122 

.31 

115 

1.52 

110 

1.73 

105 

1.91 

101 

2.08 

97 

2.22 

94 

2.37 

30 

134 

1.00 

126 

.23 

120 

1.44 

115 

1.63 

110 

1.80 

106 

1.95 

102 

2.08 

99 

2.21 

-20 

132 

1.17 

122 

1.46 

114 

1.72 

107 

1.95 

100 

2.15 

94 

2.34 

90 

2.54 

86 

2.72 

-10 

135 

1.13 

126 

1.40 

118 

1.64 

111 

1.86 

105 

2.06 

99 

2.24 

95 

2.42 

91 

2.59 

5 

0 

138 

1.06 

129 

1.32 

122 

1.56 

115 

1.77 

109 

1.96 

104 

2.14 

100 

2.31 

96 

2.46 

20 

144 

.95 

136 

1.19 

130 

1.41 

124 

1.60 

119 

1.78 

114 

1.93 

110 

2.08 

107 

2.23 

30 

148 

.91 

140 

1.13 

134 

1.33 

128 

1.51 

123 

1.67 

118 

1.80 

115 

1.96 

112 

2.10 

-20 

146 

1.06 

137 

1.34 

129 

1.59 

121 

1.81 

115 

2.02 

110 

2.22 

105 

2.40 

100 

2.56 

-10 

149 

1.02 

140 

1.28 

132 

1.52 

125 

1.73 

119 

1.93 

114 

2.12 

109 

2.29 

104 

2.44 

6 

0 

152 

.97 

143 

1.22 

135 

1.44 

129 

1.65 

123 

1.84 

118 

2.02 

113 

2.17 

109 

2.33 

20 

156 

.87 

148 

1.10 

142 

1.30 

129 

1.49 

130 

1.65 

126 

1.81 

122 

1.96 

118 

2.09 

30 

159 

.83 

151 

1.04 

145 

1.23 

139 

1.40 

134 

1.56 

130 

1.71 

126 

1.85 

122 

1.97 

-20 

159 

.98 

150 

1.25 

141 

1.47 

134 

1.69 

128 

1.90 

122 

2.08 

117 

2.26 

113 

2.44 

-10 

161 

.94 

152 

1.19 

144 

1.41 

137 

1.62 

131 

1.81 

126 

1.99 

121 

2.16 

117 

2.33 

7 

0 

163 

.90 

154 

1.13 

147 

1.35 

140 

1.54 

135 

1.73 

130 

1.90 

125 

2.06 

121 

2.22 

20 

167 

.81 

159 

1.02 

152 

1.21 

146 

1.39 

141 

1.55 

136 

1.70 

132 

1.85 

128 

1.98 

30 

169 

.76 

161 

.96 

155 

1.15 

149 

1.31 

144 

1.46 

139 

1.60 

135 

1.73 

132 

1.87 

-20 

168 

.90 

159 

1.15 

151 

1.37 

144 

1.58 

138 

1.77 

133 

.96 

128 

2.14 

123 

2.29 

-10 

170 

.87 

161 

1.10 

153 

1.31 

147 

1.51 

141 

1.69 

136 

.87 

131 

2.04 

126 

2.18 

8 

0 

172 

.83 

164 

1.05 

156 

1.25 

150 

1.44 

144 

1.62 

139 

.78 

134 

1.93 

129 

2.07 

20 

175 

.75 

167 

.94 

161 

1.13 

155 

1.30 

150 

1.46 

145 

.60 

141 

1.74 

137 

1.87 

30 

177 

.71 

169 

.89 

163 

1.07 

158 

1.23 

153 

1.38 

148 

.51 

144 

1.64 

140 

1.76 

268 


HEATING  AND  VENTILATION 


velocity  of  800  feet  per  minute  or  less  is  advisable  because  of 
the  tendency  for  the  condensation  to  freeze  in  the  coils.  The 
velocity  thus  chosen  is  used  both  as  a  basis  for  computing  the 
height  and  width  of  the  heater  and  also  for  determining  its 
depth,  i.e.,  the  number  of  stacks  to  be  used.  In  Table  XLIX 
are  given  the  final  temperatures  obtainable  from  heaters  of  vari- 
ous depths  for  air  at  different  initial  temperatures  and  velocities. 


Difference  between  Final  Temperature  and  Initial  Temperature  of  Air 


3,000 
2,500 
2,000 

1,500 


1,000 
900 
2  800 
§  700 
§  600 
I  500 
I  400 

•2  300 


200 


227Steam 


g     §    |   S|S|$SSSS.8S        S     S    38 

Frictional  Resistance  in  Inches  of  Water 
FIG.   178. — Friction  curves  for  pipe  coil  heaters. 


2.0 


The  final  temperature  for  which  the  heater  is  designed  depends 
upon  the  amount  of  heat  to  be  supplied  and  upon  whether  the 
fan  system  is  to  be  used  for  ventilating  alone  or  to  supply  the 
heating  requirements  also.  The  temperature  of  the  entering  air 
used  in  the  computations  should  be  the  minimum  for  which  the 
system  is  to  be  designed. 


DESIGN  OF  FAN  SYSTEMS 


269 


Example. — Assume  that  a  factory  is  to  be  heated  and  that  1,400,000  cubic 
feet  of  air  per  hour  are  required  at  a  temperature  of  140°.  Minimum  out- 
side temperature  0°.  What  size  Vento  heater  should  be  used? 


Free  area  (square  feet)  = 


volume  (cubic  feet  per  minute  at  70°) 


velocity  (feet  per  minute) 


Free  area  = 


1,400,000 


1200  X  60  X  1.1320 


, rorr  =  17.17  square  feet 


Difference  between  Final  Temperature  and  Initial  Temperature  of  Air, 


9.0 
8.0 
7.0 
6.0 
5.5 
5.0 
4.5 
4.0 
3.5 
£3.0 

1 

1 
a  1.0 

if 

•2  5.5 
g     .5 
0   4.5 

3.5 

..3 

2.5 

,2 

y  f^j-fo] 

for  22  7°  Steam 

~"    C       13130. 

V 

Ml 

-m 

:1 

72 

-u 
/: 

.M 

^3 

S 

5  w 

i 

C3 

2 

c- 

s  a 

OJ 

CO 

•/. 

X 

rsr- 

x 

rt 

CM 

CO 

" 

« 

*> 

;  -    d 

0 

^ 

X 

^ 

X 

0    A/1A 

\ 

; 

^ 

^ 

^ 

^ 

o 

S 

^ 

% 

s* 

X" 

^ 

x 

"  9  000 

1.94 

*ff 

«- 

^ 

I/ 

-^ 

^ 

x- 

X 

1 

xf 

I 

x 

^^ 

X 

/ 

1063  / 

nin. 

=* 

^ 

1 

^K 

^ 

^ 

x^ 

^ 

1 

1,000 

X^ 

X' 

1}'^^ 

^X^^x 

'X^xH 

^^ 

x^ 

-    9002 

800  2 

( 

X 

X 

'    ^x> 

^ 

^ 

* 

x 

^> 

^x- 

^ 

^x^ 

'x^ 

-    700  S 

^x^ 

_^ 

X 

x' 

^^' 

^  *• 

;xjx^ 

| 

.s^ 

^x^ 

^ 

^ 

;S 

x^ 

^^^ 

,  ^^ 

-    600g 

^ 

^^ 

^^- 

^ 

^ 

x;^ 

t 

^s^ 

^^ 

x^ 

x 

*s 

^^ 

-*^*f* 

*y***  w 

^^ 

^. 

^^ 

^ 

^ 

s\_ 

^_s- 

400  a 

-, 

~' 

.x 

^~, 

^ 

X. 

X 

x 

^ 

a 

^ 

X 

"  ^x 

^x; 

^ 

x^ 

^ 

s 

300  > 

x^ 

-" 

x^> 

^ 

X 

| 

^d 

^ 

^ 

-    200^ 

f 

.     0 

S8§S        !3     8    a  8 

,  Frictional  Resistance  in  Inches  of  Water 
FIG.   179.  —  Friction  curves  for  vento  heaters. 


Referring  to  Table  XLVIII  it  is  seen  that  by  using  eighteen  60-inch 
sections,  spaced  5  inches  center  to  center,  the  free  area  will  be  18  X  0.921 
=  16.58  square  feet,  which  is  sufficient,  giving  a  velocity  of  1,244  feet 
per  minute.  From  Table  XLIX  it  is  seen  that  a  heater  seven  stacks  deep 
would  raise  the  air  from  a  temperature  of  0°  to  140°  at  a  velocity  of  1,200 
feet  per  minute.  The  heater  should  therefore  be  seven  stacks  deep.  Ordi- 
narily it  would  be  divided  into  a  tempering  coil  of  three  stacks  and  a  heating 
coil  of  four  stacks. 


270  HEATING  AND  VENTILATION 

Pipe-coil  heaters  are  chosen  in  a  similar  manner  from  the  data 
furnished  by  their  manufacturers. 

Recent  tests1  have  shown  that  the  heating  effect  of  both  cast- 
iron  and  pipe-coil  heaters  is  closely  related  to  the  friction  loss 
undergone  by  the  air  in  passing  through  them;  and  that  for  the 
two  different  types  of  heaters,  the  friction  loss  will  be  practically 
identical  for  the  same  increase  in  temperature  of  the  air.  This 
might  logically  be  expected  as  the  heat  transmission  depends  upon 
the  thoroughness  of  the  rubbing  action  of  the  air  over  the  heating 
surfaces. 

From  the  curves  in  Figs.  178  and  179  the  friction  drop  can  be 
determined  for  either  Vento  or  pipe  coil  if  the  other  facts  are 
known,  and  vice  versa.  These  curves  are  based  on  the  following 
formula  which  was  developed  from  the  results  of  tests  mentioned 
above  on  pipe  coils  and  upon  tests  made  on  Vento  heaters  by 
L.  C.  Soule. 

C  =  ^      " 


KN 

in    which    C  =  condensation  in  heater — pounds  per  square  foot 

per  hour. 

V  =  velocity  of  air — feet  per  minute. 
ti  —  tz  =  temperature  rise  of  air. 
N  =  number  of  stacks  in  heater. 
K  =  a  constant  =  15,307  for  pipe  coil  and  13,130  for 
Vento. 

As  an  example  of  the  use  of  the  charts  we  will  take  an  assumed 
case.  With  five  stacks  and  an  entering  temperature  of  10°, 
the  final  temperature  for  1,200  feet  velocity  is  found  from  pipe- 
coil  data  to  be  129°,  making  the  increase  in  temperature  119°. 
In  Fig.  178  the  horizontal  dotted  line  representing  1,200  feet 
velocity  intersects  the  vertical  line  representing  119°  at  the  point 
A.  From  point  A  we  draw  the  45°  line  until  it  intersects  the 
vertical  line  for  five  stacks.  From  this  point  we  extend  a  horizon- 
tal line  to  the  right-hand  side  of  the  chart  and  we  see  that  the 
condensation  per  square  foot  per  hour  is  1.89  pounds.  The 
frictional  resistance  is  obtained  by  extending  the  horizontal  line 
for  1,200  feet  velocity  to  the  right  until  it  intersects  the  diagonal 
line  for  five  stacks;  a  vertical  line  from  this  intersection  shows  the 

1  See  "Comparison  of  Pipe  Coils  and  Cast-iron  Sections  for  Warming  Air," 
by  JOHN  R.  ALLEN,  Proc.  A.  S.  H.  &  V.  E.,  1917. 


DESIGN  OF  FAN  SYSTEMS 


271 


resistance  to  be  0.25  inch  of  water.  In  Fig.  179  the  same  case 
is  worked  out  for  Vento  heaters  as  indicated  by  the  dotted 
lines.  The  condensation  is  found  to  be  about  1.94  pounds  and 
the  velocity  1,068  feet  for  the  same  resistance  and  temperature 
rise.  It  will  be  noted  that  while  the  heating  effect  and  resistance 
of  the  two  heaters  are  the  same,  the  velocities  are  quite  different. 
234.  Installation  and  Piping  Connections. — The  heating  units 
are  usually  mounted  on  a  brick  or  concrete  pier  and  enclosed  by 
a  metal  duct.  The  proper  arrangement  of  the  steam  piping 


Trap 


By-pass 


Plate 


Center  air  vent  section 
used  when  desired. 
Recommended  for  stacks 
of  17  to  30  sections. 


3i"lron  Plate  on 
/      Top  of  Piers 


hermostatically 
Operated  Inlet  Valves 

These  air  removal 
connections  required., 
only  with  stacks 
of  17  to  24  sections) 
each. 


Thermostat! 
Air  Val 


Floor  Line 


FIG.   180. — Piping  connections  for  vento  heaters. 

connections  for  Vento  heaters  is  shown  in  Fig.  180  for  a  double- 
tier  installation.  The  center  section  of  a  long  stack  is  tapped  for 
an  air  vent  as  shown.  Separate  valves  should  be  provided  for 
each  stack  or  pair  of  stacks. 

Special  care  is  necessary  in  arranging  the  return  connections 
from  fan  heaters,  as  any  accumulation  of  condensation  will  soon 
be  frozen  by  the  cold  air.  There  is  always  a  considerable  drop 
in  pressure  through  the  heaters  and  the  inlet  connections,  so 
that  the  pressure  at  the  return  connections  should  not  be  de- 
pended upon  to  lift  the  condensation;  the  discharge  should  be  by 
gravity  or  a  vacuum  pump  should  be  used. 


272 


HEATING  AND  VENTILATION 


236.  Thermostatic  Control  for  Fan  Systems. — Thermostatic 
control  is  absolutely  necessary  on  most  types  of  fan  systems. 
Hot  blast  systems  in  factories  and  other  industrial  buildings  are 
among  the  exceptions.  The  thermostats,  located  in  the  system 
at  suitable  points,  operate  valves  on  the  supply  to  the  heating 
and  tempering  coils.  There  are  many  different  arrangements  of 
the  thermostats  and  valves  which  may  be  used,  depending  upon 
the  results  desired.  In  Fig.  181  is  shown  a  method  of  applying 
thermostatic  control  to  a  ventilating  system. 

From  Thermostat        . . 

1  '"TIT  Room  above     '     *~      ' 


FIG.  181. — Thermostatic  control  applied  to  a  fan  system. 
Problems 

1.  In  the  example  in  Par.  212,  assuming  that  657,000  cubic  feet  of  air  per 
hour  are  delivered,  if  the  heat  loss  as  given  was  computed  for  0°,  what  should 
be  the  delivery  temperature  when  the  outside  temperature  is  20°? 

2.  A  factory  building  is  to  be  heated  by  a  hot-blast  system  with  complete 
recirculation.     With  the  following  data  given  compute  the  amount  of  air 
which  must  be  handled  per  hour  by  the  system. 

Heat  loss  from  building  27,800  B.t.u.  per  hour  per  degree 

difference  in  temperature. 


Inside  temperature 
Outside  temperature 
Temperature  at  which 
air  is  delivered. 


65° 

-10° 

120° 


3.  In  the  single  duct  system  of  Fig.  166  assume  that  the  longest  duct  is  to 
carry  1100  c.f.m.     What  is   the   total   pressure   required   in  the  plenum 
chamber? 

4.  Compute  the  pipe  sizes  for  a  trunk  duct  system  similar  to  that  in  Fig. 
167  except  that  the  air  quantities  in  the  different  sections  on  a  70°  basis  are  as 
follows: 

Section  Air  quantity 

A— B  19,000  c.f.m. 

B— C  7,500 

C— D  2,000 
B— E  6,000 

E—F  4,000 
Maximum  air  temperature  130°. 


DESIGN  OF  FAN  SYSTEMS  273 

5.  Find  the  speed,  horsepower,  and  outlet  velocity  for  three  different 
sizes  of  steel  plate  fan1  delivering  18,000  c.f .m.  against  a  static  resistance 
of  13^  inches  at  70°. 

6.  Find  the  speed,  horsepower,  and  outlet  velocity  for  three  different  sizes 
of  multi-blade  fan1  delivering  12,000  c.f.m.  against  a  static  resistance  of  2 
inches  at  70°. 

7.  A  multi-blade  fan  is  to  handle  9000  c.f.m.  against  a  static  head  of  1^ 
inches  at  140°.     What  is  the  required  speed  and  horsepower? 

8.  What  would  be  the  size  of  vento  heater  required  to  heat  800,000  cubic 
feet  of  air  per  hour  from  an  outside  temperature  of  10°  to  a  delivery  tempera- 
ture of    140°?     Assume   a  velocity  through   the  heater  of  1500  feet  per 
minute. 

9.  What  would  be  the  size  of  vento  heater  required  to  heat  1,100,000  cubic 
feet  of  air  per  hour  from  an  outside  temperature  of  0°  to  a  delivery  tempera- 
ture of  70°?     Assume  a  velocity  through  the  heater  of  1100  feet  per  minute. 

10.  Find  by  means  of  the  friction  chart  in  Fig.  179  the  frictional  resistance 
of  a  vento  heater,  5  stacks  deep,  for  a  velocity  of  1500  feet  per  minute.     Find 
the  resistance  of  a  vento  heater,  3  stacks  deep,  for  a  velocity  of  900  feet  per 
minute. 

1  See  tables  in  Appendix,  pages  302  to  325. 


0  1 


CHAPTER  XVII 
AIR  WASHERS  AND  AIR  CONDITIONING 

236.  The  Air  Washer. — Various  methods  of  filtering  or  wash- 
ing air  have  been  in  use  for  many  years.  In  the  older  forms  of 
apparatus  the  dust  was  usually  filtered  from  the  air  by  means 
of  muslin  screens;  but  this  method  is  not  very  effective  and  has 
the  disadvantage  that  the  screens  soon  become  clogged  with 
dirt,  greatly  increasing  the  resistance  to  the  flow  of  air  through 
them.  Screen  filters  have  been  superseded  by  the  modern  air 
washer,  in  which  the  dirt  is  removed  from  the  air  by  water 
sprays  and  by  the  contact  of  the  air  against  wet  surfaces. 

A  typical  air  washer  is  shown  in  Fig.  182.  It  consists  of 
three  elements — the  spray  nozzles,  the  scrubber  plates,  and  the 
eliminator  plates.  The  nozzles  are  placed  in  a  bank  across  the 
path  of  the  air  and  the  water  is  forced  through  them  by  a  pump 
and  is  discharged  in  a  fine  conical  spray  or  mist  in  the  direction  of 
the  air  flow.  In  some  cases  two  banks  of  nozzles  are  used.  The 
air,  drawn  through  the  washer  by  the  fan,  is  thus  brought  into 
intimate  contact  with  the  water  and  some  of  the  dirt  and  soluble 
gases  are  removed.  The  really  effective  cleansing  is  done  by  the 
scrubber  plates  which  are  designed  to  change  the  direction  of 
flow  so  that  the  dirt  will  be  thrown  out  from  the  air  by  its  inertia 
and  by  the  rubbing  of  the  air  over  the  wet  surfaces.  The  plates 
are  kept  flooded  either  by  the  spray  nozzles  or  by  a  separate 
row  of  nozzles  placed  above  them.  Following  the  scrubber  plates 
are  a  series  of  eliminator  plates  whose  function  is  to  remove  the 
entrained  water  from  the  air.  The  lower  part  of  the  washer 
constitutes  a  tank  into  which  the  water  falls  and  from  which  it  is 
taken  by  the  circulating  pump.  A  float  valve  admits  fresh  water 
as  required  to  replace  that  evaporated. 

Proper  provision  must  be  made  in  an  air  washer  to  prevent 
trouble  from  the  large  quantities  of  dirt  which  are  washed  from 
the  air  and  deposited  in  the  tank.  A  screen  of  ample  area  is 
necessary  on  the  suction  line  to  the  pump  to  prevent  the  dirt 
from  being  carried  into  the  circulating  system,  and  in  some  types 
of  washers  special  devices  are  necessary  to  enable  the  spray 

274 


AIR  WASHERS  AND  AIR  CONDITIONS         275 


Fresh-Wat,- 
8upplj\ 


Suction  Strainer.  Drain-"" 

END  VIEW 

FIG.   182. — Air  washer. 


276  HEATING  AND  VENTILATION 

nozzles  to  be  cleaned  periodically  by  flushing.     The  accumulated 
dirt  must  be  removed  from  the  tank  at  frequent  intervals. 

The  air  washer  is  placed  between  the  tempering  coils  and  the 
heating  coils  of  a  fan  system,  this  arrangement  being  necessary 
in  order  to  insure  that  the  air  entering  the  washer  will  be  at  a 
temperature  sufficient  to  keep  the  spray  water  from  freezing. 

237.  Air  Conditioning. — The  air  washer  in  addition  to  cleans- 
ing the  air  has  other  functions.     When  properly  equipped  and 
operated  it  can  be  used  for  humidifying,  cooling,  and  dehumidi- 
fying.     In  an  ordinary  ventilating  system  it  is  commonly  used  for 
humidifying,  in  order  to  satisfy  the  ventilation  requirements 
explained  in  Chapter  XIV,  and  in  some  instances  it  is  used  for 
cooling.     Cooling  and  dehumidification,  however,  are  principally 
sought  in  industrial  applications  of  the  air  washer.     There  are 
many  industrial  processes  which  can  be  carried  on  to  much  better 
advantage  in  a  dry  atmosphere,  a  cool  atmosphere,  or  in  some 
cases  a  moist  atmosphere.     The  manufacture  and  packing  of 
certain  kinds  of  confectionery,  for  example  is  greatly  facilitated 
by  a  dry  atmosphere.     In  many  textile  processes,  and  in  the 
manufacture  of  powder,  photographic  films,  etc.,  the  proper  con- 
ditioning of  the  air  is  of  great  importance. 

238.  Humidification.  —  Humidification    is    accomplished    by 
heating  the  spray  water  so  that  the  air  will  absorb  the  proper 
amount  of  moisture  while  passing  through  the  spray  chamber. 
Sufficient  heat  is  added  to  the  spray  water,  first  to  evaporate  the 
moisture  necessary  to  bring  the  air  to  saturation  at  its  entering 
temperature  and,  second,  to  add  further  amounts  of  heat  and 
moisture  until  the  air  leaves  the  washer  at  saturation  and  at  such 
a  temperature  that  it  contains  the  requisite  quantity  of  water 
vapor.     It  then  passes  to  the  heating  coils  which  raise  its  tem- 
perature without  affecting  its  moisture  content. 

For  example,  suppose  that  it  is  required  to  deliver  air  to  a 
room  at  a  temperature  of  70°  and  a  relative  humidity  of  60  per 
cent.,  which  requires  a  moisture  content  of  4.85  grains  per  cubic 
foot.  We  will  assume  that  the  outside  air  has  a  dry-bulb  tem- 
perature of  25°  with  a  relative  humidity  of  20  per  cent.  Refer- 
ring to  Fig.  183,  the  entering  air  is  heated  by  the  tempering  coils 
to  a  temperature  of  40°,  as  represented  by  the  line  AB.  In  the 
washer  moisture  is  absorbed  from  the  spray  water  until  the  air 
becomes  saturated  at  40°,  as  represented  by  BC.  Both  heat  and 
moisture  continue  to  be  absorbed  from  the  spray  water  until  the 


AIR  WASHERS  AND  AIR  CONDITIONS 


277 


air  reaches  the  condition  represented  by  point  D,  in  which  it 
contains  4.85  grains  per  cubic  foot  and  has  a  temperature  of  55°. 
It  is  then  heated  by  the  heating  coils  to  the  delivery  temperature 
of  70°,  at  which  it  will  have  the  required  relative  humidity  of  60 
per  cent.  During  this  last  process  the  moisture  content  per 
pound  of  air  remains  the  same,  the  weight  of  the  vapor  per  cubic 
foot  decreasing  slightly  because  of  its  expansion  due  to  the  tem- 
perature increase.  For  approximate  calculations  this  difference 
may  be  neglected  and  the  line  DE  representing  this  last  step  on 


10056  90 %  80* 


20     25      30     35      40     45 


50     55      60      65     70     75 
Dry  Bulb  Temperature 
FIG.  183. 


90     95    100    105 


the  chart  in  Fig.  183  may  be  taken  as  a  horizontal  line.  For  very 
accurate  work  the  charts  in  Figs.  I  and  II  in  the  Appendix,  which 
are  constructed  on  the  basis  of  1  pound  of  air,  may  be  used. 

Every  final  condition  of  the  air  has  a  corresponding  tempera- 
ture at  saturation,  to  which  the  air  is  brought  before  it  passes  to 
the  heating  coils.  If,  in  the  case  given  above,  the  temperature  of 
the  outside  air  were  above  56°  it  would  be  lowered  because  of  the 
heat  given  up  by  it  to  evaporate  the  moisture  which  it  absorbs — 
provided,  however,  that  its  original  moisture  content  be  con- 
siderably below  saturation.  The  action  would  then  be  repre- 
sented by  the  line  FD.  If  the  dry-bulb  temperature  of  the 
entering  air  were  between  40°  and  55°  no  heat  would  be  added 


278  HEATING  AND  VENTILATION 

by  the  tempering  coil  and  moisture  would  be  added  at  a  con- 
stant dry  bulb  temperature  until  the  air  reached  saturation,  after 
which  it  would  follow  the  line  CD  to  55°  as  before. 

239.  Spray-water   Heater. — In  order  to  supply  heat  to  the 
spray  water,  a  heater  is  installed  in  the  water  circulating  line, 
between  the   pump   and  the   spray  nozzles.     If   high-pressure 
steam  is  available  it  is  injected  directly  into  the  water  through  a 
suitable  valve.     If  low-pressure  steam  or  hot  water  are  used  a 
closed   heater,   in   which   the   spray   water   circulates   through 
tubes  surrounded  by  the  heating  medium,  is  necessary. 

240.  Humidity  Control. — The  steam  supply  valve  of  the  heater 
is  controlled — usually  by  automatic  means — so  that  the  proper 


Water  Inlet 


Water  Outlet ' 
FIG.  184. — Spray- water  heater. 

amount  of  heat  is  added  to  the  water.  In  a  compressed-air 
system  of  control,  a  diaphragm  valve  is  placed  on  the  supply  to 
the  water  heater  and  may  be  operated  by  means  of  a  "hygrostat" 
or  "humidostat,"  which  corresponds  to  the  thermostat  of  a  tem- 
perature control  system.  In  place  of  the  thermostatic  element 
there  is  used  some  material  such  as  wood  or  hair  which  under- 
goes a  change  in  length  when  the  moisture  content  of  the 
surrounding  air  changes  The  " humidostat"  is  placed  either  in 
the  main  duct  or  in  the  principal  room  of  the  building  and  con- 
trols the  supply  valve  on  the  heater.  An  injector  type  of  heater 
with  a  diaphragm  control  valve  is  shown  in  Fig.  184. 

241.  Dewpoint  Method. — Another  and  a  more  rational  method 
of  humidity  control,  called  the  dewpoint  method,  is  based  on  the 
fact  that  the  air  always  leaves  the  washer  in  a  saturated  condition 
and  therefore  its  moisture  content  will  depend  upon  its  tempera- 
ture. From  a  thermostat  placed  in  the  path  of  the  air  leaving 
the  washer  the  heat  added  to  the  spray  water  is  controlled  so 
that  the  exit  temperature  of  the  saturated  air  is  at  the  point 
fixed  by  the  humidity  required.  In  the  example  given  in 
Paragraph  238  the  thermostat  at  the  washer  outlet  would  be 
set  for  55°  and  the  temperature  of  the  air  leaving  the  washer 


AIR  WASHERS  AND  AIR  CONDITIONS         279 

would  be  maintained  at  that  point.  A  special  duct-type  thermo- 
stat of  the  form  shown  in  Fig.  185  is  used  for  the  purpose, 
having  a  bulb  extending  into  the  path  of  the  air  and  controlling 
the  air  supply  to  the  diaphragm  valve  of  the  spray-water  heater. 
Humidification  may  also  be  accomplished  by  steam  jets  when  no 
washer  is  used,  in  which  case  the  jets  are  located  in  the  same 
position  as  the  washer  and  may  be  automatically  controlled. 
Another  type  of  humidifier  is  located  directly  in  the  room  and 
discharges  a  finely  atomized  "spray  which  vaporizes  after  leaving 
the  apparatus.  If  the  steam  supply  is  perfectly  free  from  oil 
and  does  not  possess  a  disagreeable  odor,  humidifiers  of  the  type 
which  discharge  stearn  directly  into  the  room  may  be  employed. 


JTo  Diaphragm  Valve  on  Spray  Water  Heater 


Stem  in  Path  of  Air 


Air  Supply 
FIG.   185. — Duct  thermostat  for  dewpoint  method  of  humidity  control. 

They  are  not  always  suitable  for  use  in  moderate  weather,  how- 
ever, as  a  considerable  amount  of  heat  is  given  up  by  the  steam 
which  might  raise  the  room  temperature  to  an  uncomfortable 
point.  The  objection  to  these  latter  forms  of  humidifier  is  the 
absence  of  automatic  means  of  regulating  the  humidity. 

242.  Cooling  by  Humidification. — If  no  heat  is  added  to  the 
spray  water  of  an  air  washer  some  evaporation  will  still  take  place 
but  the  latent  heat  of  the  vaporization  in  this  case  is  taken  from 
the  air  itself  and  the  temperature  of  the  air  is  consequently 
lowered.  The  extent  oft  the  cooling  effect  depends  upon  the 
capacity  of  the  entering  air  for  absorbing  moisture  or,  in  other 
words,  upon  the  wet-bulb  depression  of  the  entering  air.  As 
the  air  absorbs  moisture  in  the  spray  chamber  its  dry-bulb  tem- 
perature drops  but  the  wet-bulb  temperature,  which  is  a  measure 


280 


HEATING  AND  VENTILATION 


of  the  total  heat  of  the  mixture,  remains  unchanged.  If  the 
water  is  re-circulated  its  temperature  soon  drops  to  the  wet-bulb 
temperature.  In  a  perfect  washer  the  dry-bulb  temperature 
of  the  air  would  be  reduced  to  the  same  point — i.e.,  the  air 
would  become  saturated,  but  in  a  commercial  washer  this  limit 
is  never  reached.  The  cooling  effect  actually  obtained  averages 
about  60  per  cent,  of  the  wet-bulb  depression;  this  percentage 
being  termed  the  humidifying  efficiency  of  the  washer.  Referring 
to  the  psychrometric  chart  in  Fig.  186,  the  point  A  represents 
the  original  condition  of  the  air  at  90°  dry-bulb  temperature 


100#  90?  SOU    70j<     60* 


25     30      35     40      45 


50     55      60     65     70      75     80 
Dry  Bulb  Temperature 
FIG.   186. 


90      95    100    105 


and  75°  wet-bulb  temperature.  The  cooling  and  humidify- 
ing action  is  represented  by  the  constant  wet-bulb  temperature 
line  AS,  the  point  B  representing  the  final  condition  of  81° 
dry-bulb  temperature.  The  line  AC  represents  the  action  if 
the  air  were  cooled  to  saturation.  The  humidifying  efficiency 

QQ    gj 

of  the  washer  is  then  =  „„  _  -?  =  60  per  cent.,  and  the  amount 

of  moisture  actually  added  is  1.2  grains  per  cubic  foot,  or 
approximately  60  per  cent,  of  the  2.0  grains  which  it  would  be 
necessary  to  add  to  bring  the  air  to  saturation. 

For  practical  purposes,  this  method  of  cooling,  by  evaporation 


AIR  WASHERS  AND  AIR  CONDITIONS         281 

only,  has  certain  limitations.  On  hot,  humid  days  when  cooling 
in  a  ventilating  system  is  most  desired,  little  cooling  effect  can  be 
obtained  because  of  the  small  wet-bulb  depression  of  the  outside 
air.  Furthermore,  since  the  humidity  of  the  air  is  increased  and 
the  wet-bulb  temperature  unchanged,  the  cooling  power  of  the 
air  on  the  human  body  is  increased  but  little. 

243.  Cooling  and  Dehumidification  by  Refrigeration. — A 
greater  cooling  effect  can  be  obtained  if  the  spray  water  be  arti- 
ficially cooled,  in  which  case  heat  will  be  transferred  from  the  air 
to  the  water  by  direct  contact  and  no  evaporation  will  take  place. 
Both  the  dry-bulb  and  the  wet-bulb  temperatures  will  fall  until 
they  coincide  at  the  dew  point.  If  the  spray-water  temperature 
is  sufficiently  low  they  will  be  reduced  still  further  and  some  of 
the  moisture  will  be  given  up  by  the  air.  This  action  is  repre- 
sented by  the  line  ADE  in  Fig.  186.  In  a  properly  designed 
washer  the  air  can  be  cooled  to  within  a  few  degrees  of  the 
average  water  temperature.  This  method  of  dehumidification  is 
sometimes  employed  in  industrial  work.  The  air  may  be 
reheated  if  necessary  from  the  condition  indicated  by  the  point  E 
to  whatever  dry-bulb  temperature  is  required. 

A  washer  employed  for  cooling  in  this  manner  is  usually 
equipped  with  two  banks  of  spray  nozzles  through  which  the  air 
passes  successively.  The  first  bank  is  supplied  with  well  water 
or  unrefrigerated  water,  and  the  second  with  refrigerated  water. 
The  air  is  thus  given  a  preliminary  cooling  before  reaching  the 
refrigerated  water  and  the  size  of  the  refrigeration  plant  and  the 
cost  of  operation  are  reduced. 

The  refrigeration  is  accomplished  by  coils  containing  either 
brine  or  ammonia  and  placed  either  in  the  tank  of  the  washer 
or  arranged  so  that  the  water  trickles  over  them.  These  are 
called  Baudelot  coils.  In  an  air-conditioning  system  employing 
refrigeration  the  air  is  nearly  always  recirculated  because  of  the 
high  cost  of  operating  the  refrigerating  plant. 

The  problem  of  cooling  the  air  in  a  building  involves  principles 
quite  similar  to  those  of  heating.  The  amount  of  heat  which 
must  be  removed  consists  of  three  parts ;  (a)  the  heat  which  must 
be  removed  from  the  air  initially,  and  from  any  outside  air  which 
enters,  to  bring  it  to  room  temperature,  (6)  the  heat  which  enters 
through  the  walls,  roof,  etc.,  by  conduction,  and  (c)  the  heat 
which  is  generated  in  the  room  as  by  industrial  operations.  The 
air  must  be  introduced  at  a  temperature  sufficiently  below 


282  HEATING  AND  VENTILATION 

room  temperature  to  absorb  the  heat  represented  by  the  two 
latter  quantities.  The  system  might  be  thought  of  as  the 
reverse  of  a  hot  blast  heating  system. 

Problems 

1.  A  ventilating  system  has  an  air  washer  for  humidifying  and  it  is  desired 
to  maintain  a  wet-bulb  temperature  in  the  building  of  56°  and  a  dry-bulb 
temperature  of  70°.     What  must  be  the  temperature  of  the  air  as  it  leaves 
the  washer? 

2.  An  air  washer  has  a  humidifying  efficiency  of  60  per  cent.     How  many 
degrees  will  the  incoming  air  be  cooled  if  its  initial  temperature  is  87°  and 
its  dewpoint  is  65°?     What  will  be  the  final  temperature  of  the  air  after 
passing  through  a  washer  having  an  efficiency  of  58  per  cent.,  if  the  initial 
dry-bulb  temperature  is  90°  and  the  wet-bulb  temperature  is  82°? 

3.  The  outside  air  has  a  dewpoint  of  66°  and  a  temperature  of  85°.     After 
passing  through  a  washer  having  a  humidifying  efficiency  of  60  per  cent., 
what  will  be  its  dew  point  and  its  wet-bulb  temperature? 

4.  In  a  dehumidifying  system  the  incoming  air  has  a  dry-bulb  temperature 
of  85°  and  a  wet-bulb  temperature  of  72°.     What  must  be  the  dry-bulb 
temperature  of  the  air  leaving  the  washer  if  it  is  to  have  a  relative  humidity 
of  48  per  cent,  when  reheated  to  70°? 


CHAPTER  XVIII 
CENTRAL  HEATING 

244.  Classes  of  Systems. — There  are  in  general  two  classes  of 
central   heating   systems — (a)    systems   from   which   groups   of 
buildings  are  heated,  such  as  the  buildings  comprising  an  institu- 
tion,  and   (b)   systems  which  distribute  heat  commercially  to 
sections  of  cities.     The  latter  are  often  termed  district  heating 
systems.     The  general  engineering  principles  involved  are  the 
same  in  both  cases  but  there  are  many  commercial  factors  which 
enter  into  district  heating  which  do  not  enter  into  institutional 
plants.     Systems  for  institutions  are  more  commonly  met  with 
and,  unless  otherwise  noted,  the  following  text  applies  to  that 
class  of  systems.     Inasmuch  as  the  conditions  under  which  such 
systems  are  installed  differ  widely,  the  suggestions  which  follow 
can  be  but  general. 

245.  Location  of  Plant. — Before  starting  the  design  of  the 
distribution  system  it  is  necessary  to  have  a  careful  survey  made 
of  the  property,  showing  the  location  of  the  buildings  to  be  heated 
and  the  elevation  of  their  basements  and  first  floors,  together 
with  a  general  profile  of  the  ground  through  which  the  pipes  are  to 
run.     The  next  step  is  to  determine  the  proper  location  for  the 
power  plant.     In  general  the  power  plant  would  be  located  as 
near  as  possible  to  the  buildings  to  be  heated,  but  the  facilities 
for  receiving  coal  must  be  taken  into  consideration.     If  it  is 
possible  to  locate  the  plant  on  a  railroad  siding  from  which  coal 
can  be  handled  direct  from  the  cars  without-  trucking,  this  may 
prove  to  be  the  most  economical  arrangement  even  if  it  neces- 
sitates locating  the  plant  at  some  distance  from  the  buildings 
to  be  heated.     The  cost  of  loading,  trucking,  and  unloading  will 
usually  overbalance  the  investment  charges  on  the  additional 
length  of  the  pipes  required  if  the  plant  is  located  at  the  more 
distant  point. 

246.  Boilers. — The  selection  of  boilers  of  the  proper  type  and 
size  is  of  extreme  importance  in  the  economical  operation  of 
the  plant.     The  maximum  demand  for  steam  for  heating  should 

283 


284  HEATING  AND  VENTILATION 

be  computed  on  a  basis  of  the  radiation  installed  plus  a  liberal 
allowance  for  transmission  losses.  The  demand  for  steam  due 
to  the  lighting  and  power  requirements  should  be  computed  from 
a  knowledge  of  the  maximum  current  demand  and  the  steam 
consumption  of  the  electric  generating  units,  allowing  also  for 
the  energy  used  by  the  power-plant  auxiliaries.  The  boiler 
capacity  must  be  such  as  to  fill  whichever  of  the  two  requirements 
proves  to  be  the  greater.  The  exhaust  steam  should  always  be 
utilized  insofar  as  possible  for  heating.  When  the  available 
exhaust  is  not  sufficient,  some  live  steam  must  be  used,  while  if 
there  is  more  exhaust  steam  than  can  be  utilized  some  of  it  must 
be  discharged  to  atmosphere  unless  the  size  and  type  of  the 
plant  are  such  as  to  warrant  condensing  equipment. 

After  having  determined  the  maximum  amount  of  steam  which 
the  plant  might  be  called  upon  to  furnish,  the  size  of  the  boilers 
can  be  chosen.  The  steam  output  per  rated  boiler  horsepower 
varies  considerably  according  to  the  type  of  boiler,  type  of  fur- 
nace, etc.,. but  a  rough  rule  for  small  plants  is  to  assume  that  1 
square  foot  of  heating  surface  in  a  boiler  will  evaporate  3  pounds 
of  water  per  hour.  The  total  boiler  capacity  can  then  be  com- 
puted upon  this  basis  and  it  should  be  divided  into  units  of  such 
sizes  that  the  expected  range  of  loads  can  be  handled  by  operating 
the  boilers  within  their  range  of  highest  economy.  This  can  best 
be  done  by  providing  a  certain  boiler  or  boilers  to  handle  the 
lightest  loads  which  are  expected  and  other  boilers  to  handle 
the  average  operating  load  and  the  maximum  load.  It  is 
desirable  that  there  be  a  sufficient  number  of  boilers  in  the  plant 
so  that  the  largest  one  can  be  cut  out  of  service  at  any  time  for 
cleaning  or  repairs. 

If  the  boiler  pressure  to  be  carried  is  less  than  100  pounds, 
either  fire-tube  or  water-tube  boilers  may  be  used.  In  general, 
for  this  service  fire-tube  boilers  are  very  satisfactory,  as  they 
have  large  water  storage,  repairs  are  easily  made,  and  the  boiler 
may  be  operated  at  an  output  considerably  beyond  its  rated 
capacity. 

The  principal  objection  to  fire-tube  boilers,  except  those  of 
the  Scotch  marine  type,  is  the  large  space  which  they  occupy. 
If  the  boilers  are  to  be  operated  at  pressures  much  over  100 
pounds,  as  will  usually  be  the  case  if  electric  generating  units 
are  installed,  then  only  water-tube  or  Scotch  marine  boilers 
should  be  used. 


CENTRAL  HEATING  285 

247.  Systems  of  Distribution. — The   conveying  medium  for 
distributing  heat  may  be  either  steam  or  water.     Each  has  its 
advantages.     A  hot-water  system  is  very  often  used  in  hospitals 
and  similar  institutions.     Perhaps  its  greatest  advantage  is  the 
ease  in  which  the  heat  supply  can  be  controlled,  by  varying  the 
water  temperature  at  the  plant.     The  maintenance  and  operating 
attention  are  also  somewhat  less  when  the  system  has  once  been 
adjusted.     Steam  has  the  advantage  of  being  more  adaptable 
to  various  purposes  other  than  heating,  such  as  sterilizing,  cook- 
ing, and  water  heating.     It  is  also  somewhat  better  suited  for 
use  in  indirect  systems.     Furthermore,  in  case  the  plant  contains 
electric  generating  units,  it  is  always  essential  to  utilize  the 
exhaust  for  heating.     With  a  hot  water  system  it  is  necessary 
to  install  some  form  of  heater  to  transfer  the  heat  from  the 
exhaust    steam    to   the   water,    and   a   pump   to   circulate   the 
water.     With  steam  as  the  distributing  medium  this  apparatus 
is  unnecessary. 

248.  Steam   Distribution.    Gravity   System. — In   an   institu- 
tional plant  it  is  quite  important  to  return  the  condensation  to 
the  boilers,  first,  because  of  the  heat  in  the  water  which  would 
otherwise  be  wasted  and,  second,  because  the  condensation  is 
free  from  scale-forming  materials  and  is  consequently  better  for 
boiler  feed  than  raw  water.     If  the  elevation  of  the  power  plant 
with  respect  to  the  other  buildings  will  permit,  the  condensation 
may  be  returned  by  gravity  to  the  boiler  and  no  pumping  is 
necessary.     With  this  system  any  difference  in  steam  pressure 
between  the  boiler  and  the  extreme  point  in  the  piping  system  will 
result  in  a  corresponding  elevation  of  the  water  level  in  the  return 
system  at  the  extreme  point.     In  gravity  systems  it  is  usual 
to  allow  for  a  drop  in  pressure  of  not  over  2  pounds  between 
the  boiler  and  the  extreme  end  of  the  system.     In  some  cases  the 
gravity-return  system  has  been  used  over  quite  an  extended 
area,  one  building  so  heated  being  as  far  as  2,500  feet  from  the 
boiler,  and  the  system  has  given  very  good  satisfaction. 

In  a  central  heating  plant  using  the  gravity-return  system, 
unless  the  steam  mains  are  from  6  to  8  feet  above  the  return 
pipes,  it  is  necessary  that  the  steam  condensed  in  the  mains  be 
dripped  into  a  separate  return  line  and  pumped  back  to  the 
boilers,  by  a  pump  or  a  return  trap.  By  returning  the  condensa- 
tion of  the  mains  separately,  hammering  is  avoided  and  the  sys- 
tem can  be  started  much  more  rapidly. 


286  HEATING  AND  VENTILATION 

Gravity-return  systems  are  rarely  used  where  the  boiler  pres- 
sure exceeds  10  pounds. 

249.  Low-pressure  Pump  Return  System. — In  a  very  large 
system  where  it  is  difficult  to  get  enough  difference  in  elevation 
between  the  steam  and  return  mains,  or  where  the  drop  in  pres- 
sure exceeds  2  pounds,  it  is  usual  to  install  a  pump  return  system. 
This  will  usually  be  necessary  in  case  any  of  the  buildings 
are  piped  with  a  two-pipe  vapor  or  vacuum  system.     One  of  the 
common  arrangements  is  to  discharge  the  condensation  from  each 
building  through  a  trap  into  the  return  main  which  carries  the 
water  back  to  a  tank  in  the  power  house.     From  this  tank  the 
water  is  returned  to  the  boilers  by  means  of  a  pump.     The  drip 
from  the  steam  main  is  trapped  directly  to  the  return  main. 

250.  High-pressure  System. — Steam  is  sometimes  distributed 
at  high  pressure  and  the  pressure  reduced  before  entering  the 
building  piping  systems  by  means  of  a  reducing  valve.     This 
method  has  some  advantages.     Because  of  the  higher  pressure, 
the  allowable  pressure  drop  in  the  distributing  pipes  is  greatly 
increased.     This,  together  with  the  fact  that  the  specific  volume 
of  the  steam  is  less  at  the  higher  pressure,  allows  the  use  of  much 
smaller  pipes  in  the  distribution  system  and  thereby  reduces  its 
cost.     In  determining  the  size  of  the  steam  mains,  a  considerable 
drop  may  be  allowed  under  maximum  conditions,  providing  the 
pressure  at  the  most  distant  building  is  always  sufficient  to  heat 
the  building.     A  high-pressure  system  is  only  practicable  when 
there  is  no  low-pressure  exhaust  which  should  be  utilized  for 
heating. 

251.  Combination  of  Power  and  Heating  System. — In  the 
majority  of  cases  the  heating  system  is  combined  with  an  electric 
lighting  and  power  system.     The  piping  connections  may  be 
made  in  a  manner  quite  similar  to  the  arrangement  in  Fig.  125, 
page  166,  provision  being  made  to  feed  live  steam  to  the  heating 
mains  to  supplement  the  exhaust  steam  when  the  latter  is  less 
than  the  heating  requirements.     A  back-pressure  valve  should 
be  provided  to  insure  against  the  building  up  of  an  excessive 
pressure  in  the  heating  mains.     When  the  heating  load  is  very 
large  in  comparison  with  the  electrical  load,  part  of  the  boilers 
can  be  used  as  high-pressure  boilers  and  the  others  can  be  low- 
pressure  boilers  connected  directly  to  the  heating  lines.     The 
desirability  of  such  an  arrangement,  however,  is    determined 
entirely  by  local  conditions. 


CENTRAL  HEATING  287 

252.  Hot-water  Heating. — A  hot-water  system,  using  forced 
circulation,  is  very  satisfactory  if  properly  designed.     The  water 
is  heated  in  a  tube  heater  by  the  exhaust  steam  and  is  circulated 
through  the  system  by  means  of  a  centrifugal  pump.     A  vacuum 
can  be  carried  on  the  engine  exhaust  to  a  degree  depending  upon 
the  outgoing  temperature  of  the  water.     To  supplement  the 
exhaust  steam  heater  a  live  steam  heater  is  installed,  but  in  most 
cases  it  need  be  operated  only  in  the  coldest  weather.     The 
temperature  of  the  outgoing  water  is  adjusted  by  the  operating 
engineer  for  the  prevailing  weather  conditions  in  accordance 
with  a  prearranged  schedule. 

The  distribution  lines  in  a  hot-water  system  may  be  arranged 
according  to  either  of  two  schemes.  In  the  one-pipe  circuit 
system  a  single  main  makes  a  complete  circuit  of  the  territory 
covered  and  the  supply  connection  to  each  building  is  taken  from 
the  top  of  the  pipe  and  the  return  connection  is  made  to  the 
bottom  of  the  pipe  a  few  feet  further  along  and  a  resistance  is 
inserted  in  the  pipe  between  the  connections  to  divert  the  water 
into  the  building  system. 

In  the  multiple  or  two-pipe  system  both  a  flow  main  and  a 
return  main  are  installed,  the  water  passing  from  the  flow  main 
through  the  building  systems  and  back  to  the  plant  via  the  return 
main.  The  multiple  system  is  the  more  commonly  used  although 
it  is  somewhat  the  more  expensive  to  install. 

The  systems  in  the  buildings  are  arranged  in  the  ordinary 
manner  for  either  system  of  distribution. 

253.  Methods  of  Carrying  Pipes. — The  pipe  lines  serving  the 
buildings   should   always   be   carried   underground   if   possible. 
Pipes  installed  above  ground  are  extremely  unsightly  and  are 
difficult  to  support  and  to  insulate.     Underground  pipes  may 
be  installed  either  in  a  small  conduit  or  in  a  tunnel  of  walking 
height.     The  former  is  a  much  cheaper  method  and  is  quite 
satisfactory  when  only  one  or  two  pipes  are  to  be  installed,  but 
when  a  greater  number  of  pipe  lines  must  be  provided  for  or 
when  electric  cables  are  also  to  be  installed,  a  walking  tunnel  is 
desirable.     There  are  a  large  number  of  designs  of  conduits 
ranging  from  a  rough  wooden  box  to  a  heavily  insulated  and 
waterproofed  covering.     The  essential  requirements  in  a  conduit 
for  heating  pipes  are — good  insulating  qualities,  protection  of  the 
pipe  from  water,  provision  for  free  expansion  of  the  pipe,  and 
durability. 


288 


HEATING  AND  VENTILATION 


A  very  common  form  of  covering  is  the  wood  casing  shown  in 
Fig.  187.  The  casing  has  a  wall  4  inches  thick  and  is  built  of 
segmental  staves  bound  tightly  together  with  steel  or  bronze  wire, 
and  the  assembled  casing  is  rolled  in  tar  and  sawdust  to  give  it  a 
waterproof  coating  and  is  lined  with  bright  tin  to  reduce  the 
radiation  loss  from  the  pipe.  Wood  is  a  very  good  insulator  and 


FIG.   187. — Wood  casing. 

if  installed  under  favorable  conditions,  this  form  of  conduit  is 
very  satisfactory.  The  wood  deteriorates,  however,  if  sub- 
jected to  continued  dampness. 

The  concrete  conduit  shown  in  Fig.  188  has  the  advantage 
of  being  very  durable  and  is  very  easily  constructed  from  common 
materials.  The  concrete  prevents  any  considerable  amount  of 
water  from  reaching  the  pipe  and  if  desired  can  be  made  nearly 
waterproof  by  the  addition  of  a  waterproofing  compound. 


^-Standard 
^Thickness 

Pipe 
Covering 

Crushed 
Stone. 


-4  Crock 
FIG.  188. — Concrete  conduit. 

The  supports  for  the  pipe  in  any  form  of  conduit  must  be  such 
as  to  allow  it  to  move  freely  when  it  undergoes  a  change  in  length. 
Some  form  of  roller  is  commonly  used  and  they  are  placed  at 
intervals  of  10  or  15  feet. 

Another  form  of  conduit  is  built  of  vitrified  tile  split  longitudi- 
nally and  having  insulating  material  either  molded  to  the  walls 


CENTRAL  HEATING 


289 


of  the  tile  or  packed  around  the  pipe.  The  joints  are  cemented 
to  render  them  water-tight.  Such  a  conduit  is  shown  in  Fig.  189. 
There  are  many  other  types  of  construction  in  use  but  those 
which  have  been  described  are  representative.  Some  form  of 
drain  tile,  surrounded  by  a  bed  of  crushed  stone,  must  always  be 
installed  below  the  conduit  to  carry  away  the  ground  water 
to  a  sewer  or  elsewhere.  The  heat  loss  from  underground  lines 
depends  upon  the  steam  temperature,  efficiency  of  the  insulation, 
and  the  soil  conditions.  Tests  made  on  the  district  heating 
mains  of  The  Detroit  Edison  Company,  in  1913-14,  which  are 


Diatomaceous 
Insulation 


FIG.  189. — Split  tile  conduit. 

laid  in  conduit  of  the  forms  shown  in  Figs.  187  and  188,  gave  a 
result  of  0.0511  pounds  of  condensation  per  square  foot  of  external 
pipe  surface  per  hour  for  steam  at  5  pounds  pressure. 

254.  Expansion  Fittings. — Owing  to  the  length  of  the  pipe 
lines  provision  is  necessary  to  take  care  of  the  expansion.  It 
is  seldom  feasible  to  do  so  by  means  of  bends,  and  special  fittings 
are  required.  The  slip  joint  illustrated  in  Fig.  190  is  a  simple 
means  of  absorbing  large  amounts  of  expansion.  It  consists 
of  a  sleeve  which  is  free  to  move  in  the  body  of  the  fitting,  a 
packing  gland  being  provided  to  prevent  leakage.  Slip  joints 
are  located  at  intervals  of  from  200  to  300  feet  depending  upon 
the  steam  temperature.  They  must  be  installed  in  manholes 

19 


290 


HEATING  AND  VENTILATION 


or  in  some  other  place  where  they  are  accessible  for  packing. 
The  type  of  expansion  fitting  shown  in  Fig.  191  depends  upon  the 
flexibility  of  a  copper  diaphragm  for  absorbing  the  movement 
of  the  pipe.  The  advantage  of  such  a  fitting  is  that  it  requires 


FIG.  190.— Slip  joint. 

no  manhole  and  does  not  need  to  be  packed.  The  amount  of 
travel  which  can  be  allowed  for  each  fitting  is  small,  the  fittings 
being  usually  placed  at  intervals  of  80  to  100  feet  and  the  pipe 
anchored  midway  between  them.  The  body  of  the  fitting  is 


Seryice 
Outlet 


Position  of 
Diapbrame 
nd  Backin. 
Rings  when 

Pipe  is 
•Expanded.. 


_J 


Backing  Ring 


Outer  Ring 


FIG.   191. — Diaphragm  expansion  joint. 

also  anchored  and  the  expansion  of  the  pipe  on  either  side  is 
taken  up  by  the  diaphragms.  The  cost  of  a  pipe  line  fitted 
with  diaphragm  joints  is  considerably  greater  than  when  slip 
joints  are  used. 


CENTRAL  HEATING 


291 


255.  Tunnels. — Tunnels  of  brick  or  concrete  are  used  when 
several  pipes  are  to  be  carried.  The  size  and  shape  of  tunnel 
used  will  depend  upon  the  number  of  pipes  to  be  carried,  the 
character  of  the  soil,  and  the  depth  of  the  tunnel  in  the  ground. 
Fig.  192  shows  a  small  tunnel  suitable  for  pipes  of  about  8 
inches  diameter  or  less.  It  is  of  brick  4  inches  thick  and  has  a 
layer  of  Portland  cement  on  the  outside  which  is  painted  with 
a  thick  coat  of  tar  or  asphalt  over  the  arch  to  keep  out  water. 
Ribs  4  inches  thick  and  8  inches  wide  are  placed  where  the  sup- 
ports are  imbedded  in  the  walls.  The  supports  are  of  ordinary 
pipe.  A  drain  tile  may  be  placed  on  either  side  to  carry  away 


FIG.  192. 

the  ground  water  but  no  such  provision  is  necessary  if  the  tunnel 
is  built  in  a  sand  or  gravel  soil.  Owing  to  the  small  size  of  this 
tunnel  and  its  low  head  room  it  is  not  very  suitable  for  large 
pipes  or  when  much  walking  through  it  is  necessary. 

In  Fig.  193  is  shown  a  larger  tunnel  of  the  same  general  shape. 
It  is  6  feet  high  and  5  feet  wide  giving  ample  space  for  several 
pipes.  In  Fig.  194  is  shown  another  form  of  tunnel  of  still 
larger  dimensions.  The  space  under  the  walkway  is  used  for 
cable  ducts.  Pipes  can  be  installed  on  both  sides  of  the  tunnel 
if  desired.  This  shape  of  tunnel  is  not  suitable  for  use  at  con- 
siderable depths  below  the  surface  because  of  its  flat  sides, 


292 


HEATING  AND  VENTILATION 


Tllle 


FIG.  193. 


FIG.  194. 


CENTRAL  HEATING  293 

which  offer  little  resistance  against  earth  pressure.     The  horse- 
shoe shapes  previously  described  should  be  used  in  such  cases. 

256.  Size  of  Pipes. — The  size  of  steam  pipes  to  be  used  depends 
upon  the  amount  of  steam  flowing,  the  steam  pressure,  and  the 
available  pressure  drop.     If  exhaust  steam  is  used  the  pressure 
drop  is  limited  by  the  allowable  back  pressure.     In  general  it  is 
necessary  to  maintain  at  least  1^  or  2  pounds  pressure  at  each 
building  and  in  the  coldest  weather  it  may  be  necessary  to  carry 
a  still  higher  pressure,  especially  if  the  piping  in  the  buildings  is 
not  liberally  designed. 

In  underground  piping  the  noise  in  the  pipes  is  not  a  factor 
and  advantage  can  therefore  be  taken  of  all  of  the  available 
pressure  drop  to  decrease  the  size  of  the  pipes.  It  is  best,  how- 
ever, to  allow  a  reasonable  margin  in  selecting  the  pipe  sizes. 
The  chart  in  Fig.  123  is  suitable  or  pressures  of  approximately 
2  pounds.  For  higher  pressures  the  capacity  of  various  size 
pipes  for  a  given  pressure  drop  can  be  found  from  the  basic 
formula  of  Par.  139. 

For  hot-water  systems  the  pipes  sizes  can  be  computed  by 
the  methods  given  in  Chapter  XI. 

257.  Commercial    District  Heating. — The  commercial  distri- 
bution and  sale  of  heat  with  steam  or  water  as  the  conveying 
medium  is  carried  on  more  or  less  extensively  in  many  cities. 

The  use  of  hot  water  for  this  purpose  is  not  commercially 
satisfactory,  however,  because  of  the  lack  of  a  suitable  meter 
for  measuring  the  quantity  of  heat  used  by  each  consumer. 
The  more  successful  systems  are  steam  systems.  The  central 
business  districts  of  cities,  and  residence  districts  of  the  very 
highest  class  are  the  most  desirable  territory.  In  many  cases 
the  exhaust  steam  from  electric  generating  units  is  used  and 
is  distributed  at  a  pressure  of  from  2  to  10  pounds  gage.  This 
combination  produces  both  electricity  and  heat  at  a  high  thermal 
efficiency  and  from  that  standpoint  is  very  desirable,  but  there 
are  complications  resulting  which  in  some  cases  render  the 
distribution  of  live  steam,  direct  from  the  boilers,  more  feasible 
commercially. 

Distribution  systems  for  exhaust  steam  are  usually  designed 
with  a  large  trunk  main  extending  from  the  plant  through  the 
middle  of  the  heating  district,  with  branches  at  right  angles, 
taken  off  at  intervals.  The  pipes  are  laid  under  streets  and 
alleys  and  smaller  pipes  are  taken  off  to  supply  the  various 


294  HEATING  AND  VENTILATION 

buildings  heated.  In  a  live-steam  system  of  distribution  the 
same  general  method  is  often  followed,  though  the  pipes  sizes 
may  be  considerably  smaller  because  of  the  greater  density  of 
the  steam  and  the  greater  pressure  drop  allowable. 

The  general  methods  of  installing  pipes  are  the  same  as  those 
which  have  been  described.  The  condensation  is  not  usually 
returned  to  the  plant  in  a  district-heating  system  unless  raw 
water  is  very  costly  or  contains  undesirable  elements. 

The  heat  loss  from  the  underground  mains  is  an  important 
factor  and  good  insulation  is  required.  The  loss  in  distribution 
in  a  well  designed  system  is  from  15  to  25  per  cent. 

In  some  cities,  instead  of  large  areas  being  heated  from  pipes 
in  the  streets  or  alleys,  the  buildings  in  individual  blocks  are 
interconnected  and  served  with  steam  from  a  plant  in  one  of 
the  buildings. 

258.  Metering. — The  accurate   meter-ing   of  the   amount   of 
heat  supplied  to  each  consumer  is  very  important  to  the  success 
of  a  district-heating  system.     The  simplest  way  is  to  meter  the 
condensation  which  is  drained  from  the  radiators  and  which  is 
a  sufficiently  accurate  index  of  the  amount  of  heat  supplied. 
There  are  several  commercial  meters  available  for  this  purpose. 

Large  consumers  are  sometimes  metered  by  a  steam  meter 
employing  the  pitot  tube  or  venturi  principle. 

259.  Advantages  of  District  Heating. — There  are  many  advan- 
tages to  the  consumer  of  heat  purchased  from  a  central  plant 
and  to  the  community  in  which  such  a  plant  is  located.     The 
consumer  benefits  by  the  absence  of  dirt  from  the  handling 
of  coal  and  ashes  in  his  building,  by  the  saving  in  the  space 
occupied  by  a  boiler  plant,  by  the  freedom  from  labor  troubles 
and  from  uncertainties  of  fuel  supply,   and  by  the  constant 
availability  of  an  ample  and  continuous  supply  of  heat.     The 
great  benefits  to  the  community  are  the  absence  of  smoke  due 
to  the  elimination  of  the  small  isolated  boiler  plant  which  rarely 
burns  coal  smokelessly,  and  the  freedom  from  the  handling  of 
coal  and  ashes  on  the  sidewalks  and  streets. 


APPENDIX 


TABLE  I. — COEFFICIENTS    OF    HEAT    TRANSMISSION    THROUGH    BUILDING 

MATERIALS 

Walls 

BRICK  WALLS 

Coefficient  of  heat  transmission,  (k)  B.t.u.  per  square  foot  per  hour  per 
degree  difference  of  temperature. 


Thickness,  inches 


Plain 


Plastered  on  one  side  j  Furred  and  plastered 


k                                k 

k 

4 

0.52                          0.50 

0.28 

8;Hj 

0.37                          0.36 

0.23 

13 

0.29 

0.28 

0.20 

17^ 

0.25 

0.24 

0.18 

22 

0.22 

0.21 

0.16 

26^ 

0.19 

0.18 

CONCRETE  WALLS 


Thickness, 
inches 

Plain 

Furred  and 
plastered 

Thickness, 
inches 

Plain 

Furred  and 
plastered 

k 

k 

k 

k 

2 
4 

0.69 
0.55 

0.31 

16 
20 

0.37 
0.33 

0.24 
0.23 

6 

0.49 

0.30 

24 

0.30 

0.215 

8 

0.47 

0.28 

28 

0.27 

0.20 

10 

0.45 

0.265 

32 

0.25 

0.18 

12 

0.43 

0.25 

36 

0.23 

0.17 

BRICK  WALLS,  SANDSTONE  FACES 


Thickness  of 
brick,  inches 

Thickness  of 
sandstone,  inches 

k 

Thickness  of 
brick,  inches 

Thickness  of 
sandstone,  inches 

k 

4 

4                0.31 

12 

8 

0.16 

8 

4 

0.22 

4 

12 

0.26 

12 

4 

0.17 

8 

12 

0.19 

4 

8 

0.29 

12 

12 

0.15 

8 

8 

0.20 

29.3 


296 


HEATING  AND  VENTILATION 


TABLE  I. — COEFFICIENTS  OF  HEAT  TRANSMISSION  THROUGH  BUILDING 
MATERIALS  (Continued] 

Walls 
LIMESTONE  WALLS 


Thickness,  inches 

Furred  and  plastered 

Thickness,  inches 

Furred  and  plastered 

k 

k 

12 

0.49 

28 

0.31 

16 

0.43 

32 

0.28 

20 

0.38 

36 

0.26 

24 

0.35 

40 

0.24 

TILE  WALLS 


Thickness,  inches 

Plain  tile 

Tile  and  stucco 

Tile,  stucco,  and 
plaster 

k 

k 

k 

4 

0.79 

0.75 

0.34 

8 

0.56 

0.54 

0.27 

12 

0.44 

0.41 

0.26 

16 

0.40 

0.37 

0.23 

20 

0.33 

0.31 

0.20 

WOODEN  WALLS 


Clapboard  J^  g 

inch,  studding,  lath  and  plaster  

k 

0  44 

Clapboard  Y\<c 

inch,  paper,  studding,  lath  and  plaster 

0  31 

Clapboard  Jf  e 
Clapboard  J-^6 
plaster 

inch,  sheathing  %  inch,  studding,  lath  and  plaster  . 
inch,  paper,  sheathing  %  inch,  studding,  lath  and 

0.28 
0  23 

MISCELLANEOUS  WOODEN  WALLS 


Thickness  of 
board,  inches 

Pine  boards  only 

Double  boards, 
paper  between 

Board  and  corrugated 
iron 

k 

k 

fc 

X 

0.77 

0.32 

0.45 

1 

0.51 

0.24 

0.36 

m 

0.43 

0.19 

0.30 

2 

0.35 

0.16 

0.26 

W 

0.30 

0.14 

0.23 

INSIDE  PARTITIONS: 

k 

Lath  and  plaster,  one  side 0 . 60 

Lath  and  plaster,  both  sides 0 . 34 


APPENDIX  297 

TABLE.  I — COEFFICIENTS    OF    HEAT    TRANSMISSION   THROUGH  BUILDING 

MATERIALS  (Continued] 

Floors 
Floors  near  ground,  assuming  ground  temperature  =  50° 

k 

Cement  or  tile,  no  wood  above 0.31 

Cement  or  tile,  wood  above 0 . 08 

Dirt  floor 0.23 

Single  thickness  wood,  on  joists 0. 10 

Double  thickness  wood,  on  joists 0. 08 

Ceilings 

k 

Cement  or  tile,  no  wood  above 0 . 39 

Cement  or  tile,  wood  floor  above 0 . 10 

Lath  and  plaster,  no  floor  above 0 . 32 

Lath  and  plaster,  single  floor  above 0 . 26 

Metal  lath  and  plaster,  no  floor  above 0 . 49 

Roofs 
METAL  ROOFS: 

k 

Tin  on  1-inch  sap  wood  roofing  boards 0 . 45 

Copper  on  1-inch  sap  wood  roofing  boards 0 . 45 

Unlined  metal 1 . 30 

Corrugated  iron 1 . 50 

Iron  over  tongue  and  groove  boards 0 . 20 

Iron  on  wood  for  framing  only 1 . 32 

SLATE  ROOFS: 

Unlined  slate 0.82 

Slate  on  1-inch  sap  wood  roofing  boards 0 . 43 

Slate  over  tongue  and  groove  boards 0 . 30 

Slate  on  wood  for  framing  only 0 . 80 

TILE  ROOFS: 

Tile  %  to  1  inch  thick 0.80 

Tile  on  boards 0.30 

MISCELLANEOUS  : 

Shingles  on  narrow  1-inch  wood  strips 0 . 33 

Tar  paper  on  1-inch  sap  wood  roofing  boards 0 . 44 

Tar  and  gravel  over  tongue  and  groove  boards 0 . 30 

Roofs 
MISCELLANEOUS  (Continued) : 

k 

Six-inch  hollow  tile,  2-inch  concrete,  tar  and  gravel ....  0 . 36 

Same,  but  with  8-inch  tile 0 . 30 

Two-inch  concrete,  with  cinder  fill 0 . 80 

Four-inch  concrete,  with  cinder  fill 0 . 60 

Six-inch  concrete,  with  cinder  fill 0 . 54 


298 


HEATING  AND  VENTILATION 


TABLE  I. — COEFFICIENTS    OF    HEAT   TRANSMISSION  THROUGH    BUILDING 

MATERIALS  (Continued) 
Windows,  Skylights,  and  Doors 

Average  single  windows 1 . 09 

Small  size  windows  of  ordinary  glass 1 . 20 

Single  large  windows  of  plate  glass 1 . 08 

Double  windows 0 . 45 

Single-frame  windows  with  double  glass 0 . 72 

Single  skylight 1 . 50 

Double  skylight 0. 50 

Single  monitor 1 . 25 

Doors 


Thickness, 
inches 

Pine 

Oak 

Thickness, 
inches 

Pine 

Oak 

k 

k 

k 

it 

H 

0.56 

0.70 

IK 

0.36 

0.54 

H 

0.47 

0.63 

IK 

0.32 

0.50 

i 

0.41 

0.58 

2 

0.27 

0.43 

TABLE  II. — THERMAL  PROPERTIES  OF  WATER1 


Temperature, 
degrees    F. 

Specific  volume,  cubic 
feet  per  pound 

Density,  pounds 
per  cubic  foot 

Specific  heat 

20 

0.01603 

62.37 

1.0168 

30 

0.01602 

62.42 

1.0098 

40 

0.01602 

62.43 

1.0045 

50 

0.01602 

62.42 

1.0012 

60 

0.01603 

62.37 

0.9990 

70 

0.01605 

62.30 

0.9977 

80 

0.01607 

62.22 

0.9970 

90 

0.01610 

62.11 

0.9967 

100 

0.01613 

62.00 

0.9967 

110 

0.01616 

61.86 

0.9970 

120 

0.01620 

61.71 

0.9974 

130 

0.01625 

61.55 

0.9979 

140 

0.01629 

61.38 

0.9986 

150 

0.01634 

61.20 

0.9994 

160 

0.01639 

61.00 

1.0002 

170 

0.01645 

60.80 

1.0010 

180 

0.01651 

60.58 

1.0019 

190 

0.01657 

60.36 

1.0029 

200 

0.01663 

60.12 

1.0039 

210 

0.01670 

59.88 

1.0050 

220 

0.01677 

59.63 

1.007 

230 

0.01684 

59.37 

1.009 

240 

0.01692 

59.11 

1.012 

250 

0.01700 

58.83 

1.015 

1  Condensed  from  Marks  and  Davis  "Steam  Tables. 


APPENDIX  299 


PSYCHROMETRIC  CHARTS 

The  curves  in  Figs.  I  and  II1  give  the  complete  properties  of  air  based  on 
the  pound  of  air  as  a  unit.  The  curves  in  Fig.  I  are  to  be  used  for  dry-bulb 
temperatures  of  from  20°  to  110°  and  those  in  Fig.  II  for  dry-bulb  tempera- 
tures of  from  80°  to  380°.  Having  given  the  wet-  and  dry-bulb  tempera- 
tures of  the  air,  the  moisture  content  in  grains  per  pound  of  dry  air  is  found 
by  passing  vertically  from  the  dry-bulb  temperature  on  the  horizontal  scale 
to  the  diagonal  line  corresponding  to  the  wet-bulb  temperature  and  thence 
horizontally  to  the  scale  of  moisture  content  at  the  left.  The  dew  point  is 
determined  by  passing  horizontally  to  the  left  from  the  intersection  of  the 
dry-bulb  and  wet-bulb  temperature  lines  to  the  saturation  curve,  the  point 
of  intersection  being  the  dew  point.  The  heat  required  to  raise  the  tem- 
perature of  1  pound  of  air  plus  its  moisture  content  when  saturated,  and  the 
corresponding  vapor  pressure  are  found  by  passing  vertically  from  the  dew 
point  to  the  respective  curves  and  thence  to  the  corresponding  scales  at  the 
left.  The  total  heat  is  found  by  passing  vertically  from  the  wet-bulb  tem- 
perature on  the  saturation  curve  to  the  total  heat  curve  and  thence  to  the 
scale  at  the  left.  The  volume  of  air  in  cubic  feet  per  pound  for  saturated  air 
and  for  dry  air  is  obtained  by  passing  vertically  from  the  dry-bulb  tempera- 
ture to  the  respective  curves  and  to  the  scale  at  the  left. 

Example. — Assume  dry-bulb  temperature  =  75° 

relative  humidity  =  60  per  cent. 

From  the  chart  we  obtain: 

Wet-bulb  temperature,  65.25°;  dew  point,  60°;  grains  moisture  per  pound 
dry  air,  77;  heat  required  to  raise  1  pound  air  plus  its  moisture  content  when 
saturated  at  60°  through  1°,  0.247  B.t.u. 

Vapor  pressure  of  air  saturated  at  60°,  0.523  inches  mercury.  Total  heat 
in  1  pound  of  air  with  its  moisture  content  when  saturated  at  65.25°,  29.75 
B.t.u. 

As  to  this  last  quantity,  the  total  heat  of  saturated  air  at  65.25°  is  the 
same  as  that  of  the  air  under  the  given  conditions,  65.25°  being  the  wet-bulb 
temperature. 

1  From  "Fan  Engineering,"  Buffalo  Forge  Company. 


300 


HEATING  AND  VENTILATION 


OSZ 


APPENDIX 


301 


g  f,    ian:>.a^K  *°9r8q1  S1  3fnsS|2I<I  10'Z 


001 


302 


HEATING  AND  VENTILATION 


STATIC  PRESSURE  TABLES  FOR  A.  B.  C.  TYPE  S,  STEEL  PLATE  FAN 

CAPACITY  TABLE 

TABLE  III. — No.  50  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


S.  P.  Yt" 

S.  P.  %" 

S.  P.  M" 

S.  P.  X" 

S.  P.  H" 

S.  P.  %" 

Vol 

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V  Ol- 

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a 

a 

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a 

d 

ft 

id 

a 

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a 
a 

ft 
M 

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a 

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pq 

£  a 

p4 

pq 

£  a 

t"1  0) 

p4 

pq 

£  a 

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pq 

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2250 

1000 

2366 

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3610 

460 

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2475 

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2490 

317 

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2780 

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3040 

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3480 

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2700 

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3410 

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3810 

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1.09 

4180 

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1.24 

4350 

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1.34 

4275 

1900 

3546 

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3730 

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1.08 

4120 

524 

1.21 

4320 

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1.34 

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1.46 

4500 

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3700 

471 

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3860 

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1.08 

4050 

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1.20 

4255 

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1.34 

4423 

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1.47 

4580 

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1.61 

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3850 

490 

1.07 

4000 

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1.21 

4210 

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1.33 

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1.48 

4535 

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1.62 

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1.75 

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2200 

4000 

510 

1.20 

4168 

530 

1.36 

4320 

550 

1.49 

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573 

1.63 

4670 

595 

1.78 

4800 

611 

1.92 

5175 

2300 

4323 

550 

1.50 

4450 

566 

1.63 

4628 

589 

1.79 

4770 

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1.95 

4930 

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2.10 

5400 

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4460 

568 

1.62 

4620 

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1.82 

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1.97 

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5625 

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1.83 

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1.99 

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5036 

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2.32 

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2.62 

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2.98 

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5485 

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3.09 

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3.31 

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S.  P.  IK" 

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1.35 

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605 

1.61 

5040 

642 

1.85 

5330 

679 

2.11 

5625 

7172.38 

6100 

777 

2.96 

4050 

1800 

4527 

576 

1.47 

4846 

616 

1.73 

5110 

652 

1.99 

5410 

689 

2.28 

5700 

7252.55 

6195 

788 

3.15 

4275 

1900 

4613 

588 

1.60 

4945 

630 

1.87 

5230 

666 

2.14 

5520 

702 

2.44 

5780 

7372.73 

6265 

798 

3.33 

4500 

2000 

4743 

604 

1.75 

5075 

646 

2.03 

5325 

678 

2.32 

5620 

715 

2.62 

5860 

7462.92 

6365 

810 

3.53 

4725 

2100 

4850 

618 

1.89 

5145 

655 

2.19 

5440 

693 

2.49 

5724 

729 

2.81 

5955 

759 

3.12 

6475 

825 

3.76 

4950 

2200 

4970 

633 

2.07 

5256 

670 

2.365 

5550 

707 

2.68 

5790 

738 

3.00 

6050 

769 

3.32 

6550 

835 

4.00 

5175 

2300 

5090 

648 

2.345 

5370 

684 

2.565 

5630 

717 

2.88 

5900 

751 

3.22 

6150 

783 

3.54 

6610 

844 

4.24 

5400 

2400 

5210 

663 

2.447 

5480 

698 

2.770 

5750 

732 

3.09 

6025 

767 

3.44 

6270 

798 

3.78 

6700 

853 

4.50 

5625 

2500 

5340 

680 

2.655 

5610 

715 

2.970 

5850 

745 

3.32 

6100 

776 

3.67 

6343 

808 

4.04 

6800 

865 

4.76 

5850 

2600 

5485 

698 

2.875 

5740 

731 

3.22 

5980 

762 

3.56 

6200 

790 

3.92 

6460 

823 

4.31 

6880 

877 

5.04 

6300 

2800 

5710 

727)3.390 

5960 

759 

3.715 

6230 

794 

4.09 

6460 

822 

4.48 

6650 

8474.86 

7090 

903 

5.65 

6750 

3000 

5970 

7603.890 

6200 

7904.28 

6460 

822 

4.68 

6675 

850 

5.07 

6900 

879 

5.49 

7295 

928 

6.32 

7200 

3200 

6230 

7944.480 

6475 

8254.91 

6730 

857 

5.34 

6920 

881 

5.74 

7135 

909 

6.17 

7530 

960 

7.02 

7650 

3400 

6580 

8385.180 

6740 

8585.62 

6960 

886 

6.06 

7150 

910 

6.51 

7355 

937 

6.93 

7750 

987 

7.83 

8100 

3600 

6815 

8705.900 

7000 

8946.37 

7200 

916 

6.85 

7440 

948 

7.30 

7600 

968 

7.78 

8020 

1021 

8.69 

8550 

3800 

7105 

9056.730 

7350 

9367.25 

7475 

952 

7.72 

7660 

976 

8.21 

7840 

999 

8.67 

8220 

1047 

9.68 

APPENDIX 


303 


CAPACITY  TABLE 

TABLE  IV. — No.  60  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


S.  P.  K" 

S.  P.  K" 

S.  P.  K" 

S.  P.  W 

S.  P.  K"' 

S.  P.  K" 

Vnl 

1u 

V  Ol- 

ume 

73^. 

-0 

a 

ft 

-o 

a 

ft 

H 

a 

ft 

•0 

a 

ft 

1 

a 

ft 

-V 

a 

ft 

O  > 

ft  S 

A 

a  * 

d 

,J3 

•as 

ft 

^3 

ft  CD 

ft 

A 

2-| 

A 

.&! 

ft 

,£3 

£  g- 

« 

« 

H  81 

P4 

PQ 

Ha 

PS 

pq 

S  & 

rt 

ffl 

LJ  O. 

tr1  co 

« 

PQ 

••_,  Q. 

H  CQ 

P5 

pq 

3200 

1000 

2366 

251 

.287 

2690 

286 

.415 

2940 

312 

.519 

3175 

337 

.630 

3400 

361 

.743 

3610 

383 

.868 

3520 

1100 

2490 

264 

.365 

2780 

295 

.478 

3040 

323 

.593 

3267 

347 

.712 

3480 

370 

.832 

3670 

390 

.960 

3840 

1200 

2600 

276 

.435 

2925 

311 

.554 

3125 

332 

.673 

3360 

356 

.800 

3575 

379 

.932 

3763 

400 

1.06 

4160 

1300 

2736 

290 

.512 

3000 

319 

.635 

3237 

344 

.762 

3475 

369 

.900 

3675 

390 

1.04 

3865 

410 

1.18 

4480 

1400 

2846 

302 

.595 

3107 

330 

.730 

3310 

351 

.858 

3573 

379 

1.00 

3750 

398 

1.15 

3965 

421 

1.30 

4800 

1500 

2987 

317 

.697 

3226 

343 

.833 

3460 

367 

.977 

3650 

388 

1.12 

3860 

410 

1.27 

4060 

431 

1.43 

5120 

1600 

3130 

332 

.800 

3350 

356 

.948 

3565 

379 

.09 

3765 

400 

1.25 

3960 

420 

1.41 

4160 

441 

1.57 

5440 

1700 

3270 

347 

.917 

3475 

369 

1.07 

3680 

391 

.23 

3885 

413 

1.39 

4055 

431 

1.56 

4250 

451 

1.73 

5760 

1800 

3410 

362 

1.07 

3607 

382 

1.21 

3810 

405 

.38 

4010 

425 

1.55 

4180 

443 

1.76 

4350 

462 

1.92 

6080 

1900 

3546 

377 

1.19 

3730 

396 

1.37 

3935 

418 

.54 

4120 

437 

1.72 

4320 

458 

1.90 

4455 

473 

2.08 

6400 

2000 

3700 

393 

1.35 

3860 

410 

1.53 

4050 

430 

.71 

4255 

452 

1.91 

4423 

470 

2.09 

4580 

487 

2.29 

6720 

2100 

3850 

408 

1.52 

4000 

425 

1.72 

4210 

447 

.89 

4350 

462 

2.11 

4535 

481 

2.31 

4680 

498 

2.49 

7040 

2200 

4000 

425 

1.70 

4168 

443 

1.93 

4320 

458 

2.12 

4500 

478 

2.32 

4670 

497 

2.53 

4800 

510 

2.73 

7360 

2300 

4323 

459 

2.13 

4450 

473 

2.33 

4628 

491 

2.55 

4770 

507 

2.77 

4930 

523 

2.99 

7680 

2400 

4460 

473 

2.31 

4620 

490 

2.59 

4740 

504 

2.80 

4920 

522 

3.03 

5045 

537 

3.25 

8000 

2500 

4600 

488 

2.60 

4720 

502 

2.83 

4880 

518 

3.07 

5036 

534 

3.30 

5170 

549 

3.53 

8320 

2600 

4910 

521 

3.13 

5000 

531 

3.36 

5180 

550 

3.61 

5325 

565 

3.84 

8960 

2800 

5180 

550 

3.71 

5280 

560 

3.99 

5435 

578 

4.23 

5510 

585 

4.53 

9600 

3000 

5485 

582 

4.40 

5610 

596 

4.71 

5650 

600 

4.96 

5840 

620 

5.25 

S.  P.  1" 

S.  P.  IK" 

S.  P.  IK" 

S.  P.  IK" 

S.  P.  2" 

S.  P.  2K" 

TT_1 

Js 

vol- 
ume 

73  . 

ol 

•d 

a 

ft 

"S 

a 

ft 

TJ 

a 

a 

73 

a 

ft 

T3 

a 

ft 

"S 

a 

ft 

Q  > 

a£ 

ft 

,£] 

a£ 

d. 

,£3 

a£ 

a 

,J3 

ft£ 

o. 

,4 

ft$ 

ft 

^3 

a£ 

a 

,J3 

« 

w 

£  & 

t-<  to 

« 

« 

s! 

ej 

_« 

H  & 

PS 

fl 

£  ft 
r*  oo 

tf 

« 

£  ft 

t"1  CO 

« 

« 

3840 

1200 

3955 

420 

1.21 

4152 

452 

1.48 

4470 

475 

1.79 

4950 

525 

2.10 

5230 

555 

2.44 

5750 

610 

3.16 

4160 

1300 

4050 

430 

1.32 

4380 

465 

1.61 

4550 

483 

1.92 

5024 

533 

2.26 

5295 

561 

2.61 

5820 

617 

3.33 

4480 

1400 

4143 

439 

1.45 

4465 

474 

1.76 

4700 

499 

2.08 

5105 

542 

2.43 

5350 

568 

2.80 

5900 

626 

3.54 

4800 

1500 

4250 

451 

1.59 

4570 

485 

1.91 

4850 

515 

2.25 

5180 

550 

2.61 

5450 

578 

2.97 

5950 

631 

3.76 

5120 

1600 

4325 

459 

1.74 

4652 

495 

2.09 

4950 

526 

2.43 

5245 

557 

2.78 

5550 

589 

3.18 

6025 

640 

3.98 

5440 

1700 

4437 

471 

1.91 

4750 

504 

2.29 

5040 

534 

2.63 

5330 

566 

3.01 

5625 

598 

3.39 

6100 

648 

4.22 

5760 

1800 

4527 

481 

2.08 

4846 

514 

2.46 

5110 

542 

2.83 

5410 

574 

3.24 

5700 

605 

3.63 

6195 

658 

4.48 

6080 

1900 

4613 

490 

2.27 

4945 

525 

2.66 

5230 

555 

3.05 

5520 

586 

3.47 

5780 

613 

3.89 

6265 

665 

4.74 

6400 

2000 

4743 

504 

2.48 

5075 

538 

2.89 

5325 

565 

3.29 

5620 

597 

3.73 

5860 

621 

4.16 

6365 

676 

5.03 

6720 

2100 

4850 

515 

2.69 

5145 

545 

3.12 

5440 

578 

3.55 

5724 

607 

4.00 

5955 

632 

4.43 

6475 

687 

5.35 

7040 

2200 

4970 

528 

2.94 

5256 

558 

3.37 

5550 

589 

3.81 

5790 

615 

4.28 

6050 

642 

4.72 

6550 

695 

5.68 

7360 

2300 

5090 

540 

3.33 

5370 

570 

3.65 

5630 

598 

4.09 

5900 

626 

4.58 

6150 

653 

5.05 

6610 

701 

6.03 

7680 

2400 

5210 

553 

3.48 

5480 

583 

3.93 

5750 

610 

4.39 

6025 

640 

4.90 

6270 

666 

5.38 

6700 

711 

6.40 

8000 

2500 

5340 

567 

3.78 

5610 

595 

4.23 

5850 

621 

4.72 

6100 

649 

5.22 

6343 

674 

5.74 

6800 

722 

6.77 

8320 

2600 

5485 

582 

4.09 

5740 

609 

4.58 

5980 

635 

5.07 

6200 

658 

5.57 

6460 

686 

6.13 

6880 

730 

7.17 

8960 

2800 

5710 

606 

4.82 

5960 

632 

5.28 

6230 

661 

5.83 

6460 

686 

6.37 

6650 

706 

6.91 

7090 

752 

8.04 

9600 

3000 

5970 

633 

5.54 

6200 

658 

6.08 

6460 

686 

6.67 

6675 

698 

7.23 

6900 

732 

7.82 

7295 

773 

8.98 

10240 

3200 

6230 

662 

6.37 

6475 

687 

6.98 

6730 

715 

7.58 

6920 

735 

8.17 

7135 

757 

8.80 

7530 

799 

9.98 

10880 

3400 

6580 

698 

7.36 

6740 

715 

8.00 

6960 

739 

8.62 

7150 

760 

9.26 

7355 

781 

9.87 

7750 

823 

11.14 

11520 

3600 

6815 

723 

8.40 

7000 

745 

9.09 

7200 

764 

9.75 

7440 

790 

10.39 

7600 

807 

11.08 

8020 

851 

12.37 

12160 

3800 

7105 

755 

9.58 

7350 

780 

10.32 

7475 

793 

10.98 

7660 

814 

11.67 

7840 

832 

12.33 

8220 

873 

13.78 

304 


HEATING  AND  VENTILATION 


CAPACITY  TABLE 

TABLE  V. — No.  70  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


Vnl 

«• 

CD 

S.  P.  K" 

S.  P.  Hf 

S.  P.  y*" 

s.  P.  H" 

S.  P.  *i" 

S.  P.  W 

V  Ol- 

ume 

73  . 

5*3 

T3 

a 

a 

"S 

a 

a 

"S 

a 

a 

1 

8 

a 

-a 

S 

a 

"S 

8 

a 

O  > 

a£ 

a 

& 

aS 

a 

43 

&1 

a 

A 

&1 

a 

Jg 

ax 

a 

,JS 

3$ 

a 

£ 

H& 

tf 

n 

£  a 
tr1  oo 

tt 

pq 

£  a 

t-l  CO 

rt 

« 

'Ct  a 

t"1  CO 

rt 

« 

H  OB 

« 

PQ 

C  a 

t"1  CO 

« 

« 

4160 

1000 

2366 

215 

.402 

2690 

245 

.538 

2940 

267 

.674 

3175 

288 

.818 

3400 

309 

.965 

3610 

328 

1.13 

4576 

1100 

2490 

228 

.474 

2780 

253 

.622 

3040 

276 

.771 

3267 

297 

.925 

3480 

316 

1.08 

3670 

334 

1.25 

4992 

1200 

2600 

236 

.565 

2925 

266 

.719 

3125 

284 

.873 

3360 

305 

1.04 

3575 

325 

1.21 

3763 

342 

1.38 

5408 

1300 

2736 

249 

.665 

3000 

273 

.825 

3237 

294 

.992 

3475 

316 

1.17 

3675 

334 

1.35 

3865 

351 

1.53 

5824 

1400 

2846 

258 

.773 

3107 

283 

.944 

3310 

301 

.11 

3573 

325 

1.30 

3750 

341 

1.49 

3965 

361 

1.68 

6240 

1500 

2987 

271 

.905 

3226 

293 

.08 

3460 

315 

.27 

3650 

332 

1.46 

3860 

351 

1.65 

4060 

370 

1.86 

6656 

1600 

3130 

285 

1.04 

3350 

305 

.23 

3565 

324 

.42 

3765 

341 

1.62 

3960 

359 

1.83 

4160 

379 

2.04 

7072 

1700 

3270 

297 

1.19 

3475 

316 

.39 

3680 

335 

.60 

3885 

353 

1.81 

4055 

369 

2.03 

4250 

386 

2.25 

7488 

1800 

3410 

310 

1.39 

3607 

328 

.58 

3810 

346 

.79 

4010 

365 

2.01 

4180 

380 

2.28 

4350 

396 

2.49 

7904 

1900 

3546 

323 

1.55 

3730 

339 

.78 

3935 

357 

.99 

4120 

375 

2.23 

4320 

393 

2.47 

4455 

405 

2.70 

8320 

2000 

3700 

336 

1.75 

3860 

351 

.99 

4050 

368 

2.22 

4255 

387 

2.48 

4423 

402 

2.72 

4580 

417 

2.97 

8736 

2100 

3850 

350 

1.97 

4000 

364 

2.23 

4210 

383 

2.46 

4350 

396 

2.73 

4535 

413 

2.99 

4680 

426 

3.24 

9152 

2200 

4000 

364 

2.21 

1168 

379 

2.50 

4320 

393 

2.75 

4500 

410 

3.02 

4670 

425 

3.29 

4800 

436 

3.55 

9568 

2300 

1323 

393 

2.77 

4450 

405 

3.02 

4628 

421 

3.30 

4770 

433 

3.60 

4930 

448 

3.88 

9984 

2400 

4460 

406 

2.99 

4620 

420 

3.36 

4740 

430 

3.63 

4920 

447 

3.93 

5045 

459 

4.22 

10400 

2500 

1600 

418 

3.37 

4720 

430 

3.68 

4880 

443 

3.99 

5036 

458 

4.28 

5170 

470 

4.59 

10816 

2600 

4910 

446 

4.07 

5000 

455 

4.37 

5180 

471 

4.69 

5325 

483 

4.98 

11648 

2800 

5180 

471 

4.82 

5280 

480 

5.19 

5435 

491 

5.50 

5510 

501 

5.88 

12480 

3000 

5485 

499 

5.71 

5610 

511 

6.12 

5650 

514 

6.43 

5840 

530 

6.82 

S.  P.  1" 

S.  P.  IK" 

S.  P.  1H" 

S.  P.  W 

S.  P.  2" 

S.  P.  2K" 

Vnl 

O 

V  Ol- 

ume 

"3  "3 

O  > 

1 

a 

a 

a 

al 

a 

a 

a 

"0 

a 

a 

a 

al 

a 

a 

a 

| 

a 

a 

a 

T3 

a 

a 

0, 

H& 

pq 

H! 

pq 

nit 

pq 

s! 

pq 

EH  ft 

« 

EH  co 

». 

4992 

1200 

3955 

359 

1.57 

4152 

378 

1.92 

4470 

407 

2.33 

4950 

450 

2.72 

5230 

475 

3.17 

5750 

523 

4.11 

5408 

1300 

4050 

368 

1.71 

4380 

398 

2.09 

4550 

415 

2.50 

5024 

457 

2.93 

5295 

481 

3.39 

5820 

529 

4.32 

5824 

1400 

4143 

376 

1.88 

4465 

406 

2.28 

4700 

427 

2.71 

5105 

465 

3.15 

5350 

487 

3.63 

5900 

536 

4.59 

6240 

1500 

4250 

386 

2.07 

4570 

416 

2.48 

4850 

441 

2.91 

5180 

471 

3.38 

5450 

495 

3.86 

5950 

541 

4.88 

6656 

1600 

4325 

393 

2.26 

4652 

424 

2.71 

4950 

450 

3.15 

5245 

476 

3.61 

5550 

505 

4.13 

6025 

548 

5.17 

7072 

1700 

4437 

404 

2.47 

4750 

432 

2.97 

5040 

459 

3.42 

5330 

484 

3.90 

5620 

511 

4.41 

6100 

555 

5.47 

7488 

1800 

4527 

412 

2.70 

4846 

440 

3.19 

5110 

465 

3.67 

5410 

494 

4.21 

5700 

519 

4.72 

6195 

563 

5.82 

7904 

1900 

4613 

420 

2.95 

4945 

449 

3.45 

5230 

475 

3.96 

5520 

502 

4.52 

5780 

525 

5.05 

6265 

570 

6.15 

8320 

2000 

4743 

430 

3.22 

5075 

461 

3.75 

5325 

484 

4.28 

5620 

511 

4.84 

5860 

533 

5.40 

6365 

579 

6.52 

8736 

2100 

4850 

441 

3.50 

5145 

468 

4.05 

5440 

494 

4.61 

5724 

521 

5.20 

5955 

541 

5.76 

6475 

588 

6.95 

9152 

2200 

4970 

452 

3.81 

5256 

477 

4.37 

5550 

505 

4.96 

5790 

527 

5.55 

6050 

550 

6.13 

6550 

595 

7.38 

9568 

2300 

5090 

463 

4.33 

5370 

488 

4.74 

5630 

512 

5.32 

5900 

536 

5.95 

6150 

560 

6.55 

6610 

601 

7.82 

9984 

2400 

5210 

474 

4.52 

5480 

498 

5.11 

5750 

523 

5.70 

6025 

547 

6.36 

6270 

570 

6.98 

6700 

610 

8.32 

10400 

2500 

5340 

485 

4.91 

5610 

510 

5.49 

5850 

532 

6.13 

6100 

555 

6.78 

6343 

575 

7.46 

6800 

618 

8.80 

10816 

2600 

5485 

498 

5.32 

5740 

522 

5.95 

5980 

544 

6.58 

6200 

564 

7.23 

6460 

587 

7.96 

6880 

625 

9.32 

11648 

2800 

5710 

520 

6.26 

5960 

542 

6.85 

6230 

567 

7.57 

6460 

587 

8.28 

6650 

605 

8.98 

7090 

644 

10.44 

12480 

3000 

5970 

542 

7.19 

6200 

564 

7.90 

6460 

598 

8.66 

6675 

607 

9.38 

6900 

627 

10.13 

7295 

663 

11.65 

13312 

3200 

6230 

567 

8.27 

6475 

588 

9.07 

6730 

612 

9.86 

6920 

629 

10.60 

7135 

648 

11.40 

7530 

685 

12.97 

14144 

3400 

6580 

598 

9.58 

6740 

613 

10.38 

6960 

632 

11.19 

7150 

650 

12.00 

7355 

670 

12.81 

7750 

705 

14.46 

14976 

3600 

6815 

620 

10.88 

7020 

638 

11.77 

7200 

655 

12.66 

7440 

676 

13.48 

7600 

691 

14.38 

8020 

729 

16.04 

15808 

3800 

7105 

646 

12.43 

7350 

668 

13.40 

7475 

680 

14.25 

7660 

697 

15.14 

7840 

713 

16.00 

8220 

747 

17.88 

APPENDIX 


305 


CAPACITY  TABLE 
TABLE  VI.— No.  80  SINGLE  INLET  STEEL  PLATE  FAN— TYPE  S 


Vol- 

S. P.  K" 

S.  P.  W 

S.  P.  W 

S.  P.  H" 

s.  P.  ys 

S.  P.  %" 

ume 

3* 

•a 

8 

a 

•a 

a 

a 

•a 

8 

a 

•a 

8 

a 

•a 

8 

a 

"& 

6 

a 

0> 

&1 

p, 

jg 

a£ 

a 

,ig 

a  1 

a 

,£5 

2-1 

a 

A 

8-1 

a 

M 

&i 

a 

J3 

^a 

tf 

« 

^g* 

tf 

pq 

Ha 

tf 

« 

^& 

« 

pq 

^a 

« 

P5 

H& 

tf 

pq 

5050 

1000 

2366 

189 

.488 

2690 

214 

.654 

2940 

234 

.818 

3175 

253 

.994 

3400 

271 

1.17 

3610 

288 

1.37 

5555 

1100 

2490 

198 

.575 

2780 

222 

.755 

3040 

242 

.935 

3267 

260 

1.12 

3480 

277 

1.31 

3670 

292 

1.52 

6060 

1200 

2600 

207 

.685 

2925 

233 

.873 

3125 

249 

1.06 

3360 

268 

1.26 

3575 

285 

1.47 

3763 

300 

1.68 

6565 

1300 

2736 

218 

.808 

3000 

239 

1.002 

3237 

257 

1.21 

3475 

276 

1.42 

3675 

292 

1.63 

3865 

308 

1.86 

7070 

1400 

2846 

227 

.940 

3107 

248 

1.144 

3310 

264 

1.35 

3573 

285 

1.58 

3750 

299 

1.81 

3965 

316 

2.05 

7575 

1500 

2987 

238 

1.097 

3226 

257 

1.314 

3460 

276 

1.54 

3650 

291 

1.77 

3860 

307 

2.01 

4060 

324 

2.26 

8080 

1600 

3130 

250 

1.263 

3350 

267 

1.497 

3565 

284 

1.73 

3765 

298 

1.97 

3960 

315 

2.22 

4160 

332 

2.48 

8585 

1700 

3270 

261 

1.445 

3475 

277 

1.695 

3680 

293 

1.94 

3885 

310 

2.19 

4055 

323 

2.47 

4250 

339 

2.74 

9090 

1800 

3410 

272 

1.686 

3607 

287 

1.920 

3810 

303 

2.18 

4010 

319 

2.44 

4180 

333 

2.77 

4350 

347 

3.02 

9595 

1900 

3546 

283 

1.878 

3730 

297 

2.165 

3935 

313 

2.42 

4120 

328 

2.71 

4320 

344 

3.00 

4455 

350 

3.28 

10100 

2000 

3700 

295 

2.150 

3860 

305 

2.425 

4050 

322 

2.71 

4255 

339 

3.01 

4423 

353 

3.31 

4580 

365 

3.61 

10605 

2100 

3850 

307 

2.400 

4000 

319 

2.71 

4210 

335 

2.99 

4350 

347 

3.33 

4535 

361 

3.64 

4680 

373 

3.94 

11110 

2200 

4000 

319 

2.688 

4168 

332 

3.04 

4320 

344 

3.34 

4500 

358 

3.67 

4670 

372 

4.00 

4800 

383 

4.32 

11615 

2300 

4323 

345 

3.36 

4450 

354 

3.67 

4628 

369 

4.02 

4770 

380 

4.37 

4930 

393 

4.71 

12120 

2400 

4460 

356 

3.63 

4620 

368 

4.08 

4740 

378 

4.42 

4920 

393 

4.78 

5045 

402 

5.12 

12625 

2500 

4600 

367 

4.10 

4720 

376 

4.47 

4880 

389 

4.85 

5036 

401 

5.20 

5170 

412 

5.57 

13130 

2600 

4910 

392 

4.94 

5000 

398 

5.30 

5180 

413 

5.69 

5325 

423 

6.06 

14140 

2800 

5180 

413 

5.85 

5280 

421 

6.30 

5435 

433 

6.67 

5510 

439 

7.14 

15150 

3000 

1 

| 

5485 

437 

6.93 

56K 

447 

7.42 

5650 

450 

7.81 

5840 

465 

8.28 

Vnl 

S.  P.  1" 

STJ   -11  /// 
.  r.  l^i 

s.  P.  iy2" 

S.  P.  1M" 

S.  P.  2" 

S.  P.  2M" 

V  Ol- 

ume 

ll 

al 

a 

a 

a 
jt 

-d 

a 

a 

a 

al 

a 

a 

^ 

T3 

a 

a 

a 

A 

•1 

3 
a 

a 

,£3 

al 

a 

a 

a 

,£3 

•^  TO 

P4 

pq 

£  &• 

fl  00 

p4 

pq 

£  °- 

"^  m 

« 

pq 

ft 

"•  TO 

tf 

pq 

£  a 

•*  TO 

pq 

sl 

pq 

6060 

1200 

3955 

315 

1.91 

4152 

331 

2.33 

4470 

356 

2.83 

4950 

394 

3.31 

5230 

417 

3.86 

5750 

458 

5.00 

6565 

1300 

4050 

322 

2.08 

4380 

349 

2.54 

4550 

363 

3.03 

5024 

400 

3.56 

5295 

421 

4.12 

5820 

464 

5.25 

7070 

1400 

4143 

329 

2.28 

4465 

356 

2.77 

4700 

375 

3.29 

5105 

407 

3.83 

5350 

426 

4.42 

5900 

470 

5.58 

7575 

1500 

4250 

338 

2.51 

4570 

364 

3.02 

4850 

386 

3.54 

5180 

413 

4.10 

5450 

434 

4.68 

5950 

475 

5.93 

8080 

1600 

4325 

345 

2.75 

4652 

371 

3.29 

4950 

395 

3.83 

5245 

418 

4.39 

5550 

442 

5.02 

6025 

480 

6.27 

8585 

1700 

4437 

353 

3.01 

4750 

378 

3.61 

5040 

402 

4.15 

5330 

424 

4.74 

5625 

448 

5.35 

6100 

486 

6.63 

9090 

1800 

4527 

361 

3.29 

4846 

386 

3.89 

5110 

407 

4.46 

5410 

431 

5.10 

5700 

455 

5.73 

6195 

493 

7.05 

9595 

1900 

4613 

368 

3.59 

4945 

394 

4.19 

5230 

417 

4.81 

5520 

440 

5.48 

5780 

460 

6.13 

6265 

499 

7.47 

10100 

2000 

4743 

377 

3.91 

5075 

404 

4.55 

5325 

424 

5.19 

5620 

448 

5.88 

5860 

467 

6.57 

6365 

507 

7.92 

10605 

2100 

4850 

386 

4.25 

5145 

410 

4.92 

5440 

433 

5.60 

5724 

456 

6.32 

5955 

475 

7.00 

6475 

516 

8.45 

11110 

2200 

4970 

396 

4.64 

5256 

419 

5.31 

5550 

443 

6.02 

5790 

461 

6.74 

6050 

482 

7.45 

6550 

522 

8.96 

11615 

2300 

5090 

405 

5.36 

5370 

427 

5.75 

5630 

448 

6.45 

5900 

470 

7.22 

6150 

490 

7.95 

6610 

527 

9.52 

12120 

2400 

5210 

416 

5.48 

5480 

437 

6.20 

5750 

458 

6.92 

6025 

480 

7.72 

6270 

500 

8.48 

6700 

534 

10.10 

12625 

2500 

5340 

425 

5.96 

5610 

447 

6,66 

5850 

466 

7.45 

6100 

486 

8.23 

6343 

505 

9.06 

6800 

542 

10.68 

13130 

2600 

5485 

437 

6.44 

5740 

457 

7.22 

5980 

477 

7.98 

6200 

494 

8.78 

6460 

515 

9.67 

6880 

548 

11.30 

14140 

2800 

5710 

455 

7.60 

5960 

475 

8.33 

6230 

497 

9.19 

6460 

515 

10.05 

6650 

530 

10.90 

7090 

564 

12.68 

15150 

3000 

5970 

476 

8.73 

6200 

494 

9.60 

6460 

515 

10.53 

6675 

532 

11.38 

6900 

550 

12.33 

7295 

581 

14.16 

16160 

3200 

6230 

497 

10.05 

6475 

517 

11.00 

6730 

537 

11.97 

6920 

551 

12.88 

7135 

568 

13.86 

7530 

600 

15.73 

17179 

3400 

6580 

524 

11.62 

6740 

537 

12.62 

6960 

555 

13.60 

7150 

570 

14.60 

7355 

587 

15.55 

7750 

618 

17.58 

18180 

3600 

6815 

543 

13.23 

7000 

559 

14.30 

7200 

574 

15.40 

7440 

593 

16.38 

7600 

605 

17.48 

8020 

639 

19.50 

19190 

3800 

7105 

565 

15.10 

7350 

586 

16.27 

7475 

596 

17.30 

7660 

611 

18.38 

7840 

624 

19.44 

8220 

655 

21.73 

20 


306 


HEATING  AND  VENTILATION 


CAPACITY  TABLE 
TABLE  VII. — No.  90  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


S.  P.  tf  " 

S.  P.  W 

S.  P.  Y2" 

S.  P.  H" 

S.  P.  H" 

S.  P.  %" 

Vol- 

<_> 

ume 

3'3 

"8 

a 

a 

"8 

3 

a 

2 

a 

a 

73 

a 

a 

"8 

a 

a 

S 

8 

a 

O> 

a£ 

a 

,q 

P,£ 

a 

43 

a$ 

a 

A 

a£ 

a 

43 

a£ 

a 

jt 

a£ 

a 

43 

^£ 

& 

pq 

H  & 

P? 

pq 

C  ft 

r*1  to 

pj 

pq 

H& 

P3 

pq 

J  a 

tr1  <n 

« 

pq 

H& 

« 

pq 

6450 

1000 

2366 

167 

.625 

2690 

190 

.835 

2940 

208 

.05 

3175 

224 

1.27 

3400 

240 

1.49 

3610 

255 

1.75 

7095 

1100 

2490 

176 

.735 

2780 

196 

.965 

3040 

215 

.19 

3267 

231 

1.43 

3480 

246 

1.68 

3670 

259 

1.93 

7740 

1200 

2600 

184 

.876 

2925 

207 

1.11 

3125 

221 

.35 

3360 

238 

1.61 

3575 

253 

1.88 

3763 

266 

2.14 

8385 

1300 

2736 

193 

1.03 

3000 

212 

1.27 

3237 

229 

.54 

3475 

245 

1.81 

3675 

259 

2.09 

3865 

273 

2.37 

9030 

1400 

2846 

201 

1.20 

3107 

220 

1.46 

3310 

234 

.73 

3573 

253 

2.03 

3750 

265 

2.31 

3965 

280 

2.61 

9675 

1500 

2987 

211 

1.40 

3226 

228 

1.68 

3460 

244 

1.97 

3650 

258 

2.26 

3860 

273 

2.57 

4060 

287 

2.89 

10320 

1600 

3130 

221 

1.61 

33,50 

237 

1.91 

3565 

252 

2.21 

3765 

266 

2.52 

3960 

280 

2.84 

4160 

294 

3.17 

10965 

1700 

3270 

231 

1.85 

3475 

245 

2.17 

3880 

260 

2.48 

3885 

275 

2.81 

4055 

287 

3.15 

4250 

300 

3.49 

11610 

1800 

3410 

241 

2.15 

3607 

255 

2.45 

3810 

269 

2.79 

4010 

283 

3.12 

4180 

296 

3.54 

4350 

308 

3.86 

12255 

1900 

3546 

251 

2.40 

3730 

264 

2.76 

3935 

278 

3.10 

4120 

291 

3.46 

4320 

305 

3.83 

4455 

315 

4.19 

12900 

2000 

3700 

262 

2.72 

3860 

273 

3.09 

4050 

286 

3.46 

4255 

301 

3.86 

4423 

313 

4.22 

4580 

324 

4.62 

13545 

2100 

3850 

272 

3.06 

4000 

283 

3.47 

4210 

298 

3.82 

4350 

308 

4.25 

4535 

320 

4.64 

4680 

331 

5.03 

14190 

2200 

4000 

283 

3.43 

4168 

295 

3.88 

4320 

305 

4.27 

4500 

318 

4.68 

4670 

330 

5.11 

4800 

340 

5.52 

14835 

2300 

4323 

306 

4.30 

4450 

314 

4.69 

4628 

327 

5.13 

4770 

338 

5.59 

4930 

348 

6.02 

15480 

2400 

4460 

315 

4.64 

4620 

327 

5.21 

4740 

335 

5.65 

1920 

348 

6.22 

5045 

356 

6.55 

16125 

2500 

4600 

325 

5.24 

4720 

334 

5.71 

4880 

347 

6.19 

5036 

356 

6.64 

5170 

366 

7.13 

16770 

2600 

4910 

348 

6.31 

5000 

354 

6.77 

5180 

366 

7.28 

5325 

376 

7.74 

18060 

2800 

5180 

366 

7.47 

5280 

373 

8.05 

5435 

384 

8.53 

5510 

390 

9.12 

19350 

3000 

5485 

387 

8.87 

5610 

397 

9.48 

5650 

400 

9.98 

5840 

414 

10.57 

S.  P.  1" 

S.  P.  IK" 

S.  P.  1W 

S.  P.  W 

S.  P.  2" 

S.  P.  2Y2" 

Vol- 

^> 

ume 

3  . 

3*3 

"8 

a 

ft 

H 

a 

.  p, 

TJ 

8 

ft 

"S 

a 

ft 

•0 

a 

ft 

•Sj 

8 

ft 

0> 

&1 

a 

43 

&1 

4 

43 

&! 

a 

43 

&i 

ft 

43 

a£ 

ft 

43 

as 

a 

43 

Sg 

« 

e 

£& 

rt 

pq 

Ha 

p4 

pq 

^& 

rt 

pq  ' 

H  §* 

« 

« 

£  a 

T1  CO 

Ptj 

pq 

7740 

1200 

3955 

279 

2.44 

4152 

294 

2.98 

4470 

316 

3.61 

4950 

350 

4.23 

5230 

370 

4.93 

5750 

406 

6.38 

8385 

1300 

4050 

286 

2.65 

4380 

309 

3.25 

4550 

322 

3.88 

5024 

353 

4.56 

5295 

374 

5.26 

5820 

411 

6.71 

9030 

1400 

4143 

293 

2.92 

4465 

316 

3.55 

4700 

332 

4.21 

5105 

361 

4.88 

5350 

378 

5.65 

5900 

417 

7.13 

9675 

1500 

4250 

300 

3.21 

4570 

323 

3.86 

4850 

343 

4.53 

5180 

366 

5.24 

5450 

385 

5.98 

5950 

420 

7.57 

10320 

1600 

4325 

306 

3.51 

4652 

329 

4.21 

4950 

350 

4.89 

5245 

370 

5.61 

5550 

392 

6.41 

6025 

427 

8.02 

10965 

1700 

4437 

313 

3.84 

4750 

336 

4.61 

5040 

356 

5.31 

5330 

377 

6.06 

5625 

398 

6.83 

6100 

431 

8.48 

11610 

1800 

4527 

320 

4.20 

4846 

342 

4.96 

5110 

362 

5.70 

5410 

383 

6.52 

5700 

403 

7.32 

6195 

438 

9.02 

12255 

1900 

4613 

327 

4.58 

4945 

350 

5.35 

5230 

370 

6.15 

5520 

393 

7.00 

5780 

408 

7.82 

6265 

443 

9.55 

12900 

2000 

4743 

335 

5.00 

5075 

359 

5.81 

5325 

377 

6.63 

5620 

398 

7.52 

5860 

415 

8.38 

6365 

450 

10.12 

13545 

2100 

4850 

343 

5.43 

5145 

364 

6.29 

5440 

384 

7.15 

5724 

405 

8.07 

5955 

421 

8.94 

6476 

458 

10.78 

14190 

2200 

4970 

352 

5.82 

5256 

372 

6.78 

5550 

393 

7.70 

5790 

409 

8.62 

6050 

428 

9.52 

6550 

463 

11.45 

14835 

2300 

5090 

360 

6.61 

5370 

380 

7.35 

5630 

398 

8.25 

5900 

417 

9.23 

6150 

435 

10.15 

6610 

467 

12.13 

15480 

2400 

5210 

369 

7.01 

5480 

387 

7.92 

5750 

406 

8.85 

6025 

427 

9.87 

6270 

442 

10.84 

6700 

474 

12.88 

16125 

2500 

5340 

377 

7.62 

5610 

396 

8.52 

5850 

413 

9.52 

6100 

432 

10.50 

6343 

449 

11.96 

6800 

480 

13.63 

16770 

2600 

5485 

388 

8.25 

5740 

405 

9.22 

5980 

424 

10.20 

6200 

438 

11.22 

6460 

456 

2.35 

6880 

487 

14.44 

18060 

2800 

5710 

404 

9.72 

5960 

422 

10.65 

6230 

441 

11.74 

6460 

457 

12.83 

6650 

470 

13.73 

7090 

501 

16.20 

19350 

3000 

5970 

422 

11.15 

6200 

438 

12.25 

6460 

457 

13.45 

6675 

472 

14.55 

6900 

488 

15.73 

7295 

515 

18.05 

20640 

3200 

6230 

441 

12.83 

6475 

451 

14.05 

6730 

476 

15.30 

6920 

489 

16.44 

7135 

503 

17.70 

7530 

533 

20.10 

21930 

3400 

6580 

465 

14.85 

6740 

477 

16.10 

6960 

492 

17.35 

7150 

505 

18.65 

7355 

519 

19.86 

7750 

548 

22.45 

23220 

3600 

6815 

482 

16.90 

7020 

497 

18.25 

7200 

510 

19.65 

7440 

525 

20.92 

7600 

538 

22.30 

8020 

567 

24.87 

24510 

3800 

7105 

503 

19.30 

7350 

520 

20.75 

7475 

528 

22.13 

7660 

542 

23.53 

7840 

554 

24.85 

8220 

581 

27.75 

APPENDIX 


307 


CAPACITY  TABLE 

TABLE  VIII.— No.  100  SINGLE  INLET  STEEL  PLATE  FAN— TYPE  S 


Vol- 

S. P.  Ji" 

S.  P.  %" 

S.  P.  W 

S.  P.  %" 

S.  P.  X" 

S.  P.  K" 

ume 

"3  75 

"8 

a 

ft 

"8 

a 

^3 

TJ 

a 

ft 

"8 

a 

ft 

"8 

a 

ft 

1 

a 

ft 

0> 

ftcp 

P. 

.8-8 

p. 

ft 

ft  o> 

& 

8-1 

d 

8-1 

ft 

e-I 

ft 

H  « 

pi 

PQ 

tj  ^ 

t"1  CO 

« 

PQ 

H  & 

PS 

» 

£  ft 

C*  co 

p4 

PQ 

£  ft 

f  CO 

tf 

PQ 

pi 

PQ 

8260 

1000 

2366 

150 

.800 

2890 

171 

1.07 

2940 

187 

1.34 

3175 

202 

1.62 

3400 

216 

1.92 

3610 

230 

2.24 

9086 

1100 

2490 

158 

.942 

2780 

177 

1.23 

3040 

193 

1.53 

3267 

208 

1.84 

3480 

221 

2.15 

3670 

234 

2.47 

9912 

1200 

2600 

165 

1.12 

2925 

186 

1.43 

3125 

199 

1.73 

3360 

214 

2.06 

3575 

227 

2.40 

3763 

240 

2.74 

10738 

1300 

2736 

174 

1.32 

3000 

191 

1.64 

3237 

206 

1.97 

3475 

221 

2.37 

3675 

233 

2.67 

3865 

246 

3.03 

11564 

1400 

2846 

181 

1.53 

3107 

198 

1.87 

3310 

211 

2.21 

3573 

227 

2.59 

3750 

239 

2.96 

3965 

252 

3.35 

12390 

1500 

2987 

190 

1.79 

3226 

205 

2.14 

3460 

220 

2.52 

3650 

233 

2.90 

3860 

246 

3.28 

4060 

258 

3.69 

13216 

1600 

3130 

199 

2.06 

3350 

213 

2.44 

3565 

227 

2.82 

3765 

240 

3.23 

3960 

252 

3.63 

4160 

265 

4.07 

14042 

1700 

3270 

208 

2.37 

3475 

222 

2.77 

3680 

234 

3.17 

3885 

247 

3.59 

4055 

258 

4.03 

4250 

270 

4.47 

14868 

1800 

3410 

217 

2.75 

3607 

230 

3.14 

3810 

242 

3.57 

4010 

255 

3.99 

4180 

266 

4.53 

4350 

277 

4.95 

15694 

1900 

3546 

226 

3.07 

3730 

237 

3.54 

3935 

252 

3.97 

4120 

262 

4.43 

4320 

275 

4.90 

4455 

284 

5.37 

16520 

2000 

3700 

235 

3.47 

3860 

245 

3.97 

4050 

9,'jS 

4.43 

4255 

269 

4.93 

4423 

282 

5.41 

4580 

292 

5.90 

17346 

2100 

3850 

245 

3.92 

4000 

254 

4.43 

4210 

208 

4.88 

4350 

277 

5.44 

4535 

289 

5.95 

4680 

298 

6.44 

18172 

2200 

4000 

254 

4.39 

4168 

265 

4.97 

4320 

27,5 

5.47 

4500 

286 

6.00 

4670 

297 

6.54 

4800 

306 

7.06 

18998 

2300 

4323 

275 

5.50 

4450 

283 

6.01 

4628 

294 

6.57 

4770 

303 

7.15 

4930 

314 

7.70 

19824 

2400 

4460 

284 

5.95 

4620 

294 

6.67 

4740 

302 

7.23 

4920 

313 

7.82 

5045 

321 

8.38 

20650 

2500 

4600 

293 

6.70 

4720 

301 

7.32 

4880 

310 

7.92 

5036 

320 

8.52 

5170 

329 

9.13 

21478 

2600 

4910 

312 

9.08 

5000 

318 

8.52 

5180 

329 

9.33 

5325 

339 

9.92 

23128 

2800 

5180 

330 

9.57 

5280 

338 

10.30 

5435 

346 

10.92 

5510 

351 

11.67 

24780 

3000 

5485 

349 

11.34 

5610 

357 

12.14 

5650 

359 

12.77 

5840 

371 

13.53 

TT^I 

S.  P.  1" 

S.  P.  IK" 

S.  P.  IK" 

S.  P.  IK" 

S.  P  2" 

S.  P.  2M" 

Vol- 
ume 

5*3 

-| 

a 

ft 

ft^ 

a 

ft 

pi 

a 

cL 

ft 

•d 

a 

ft 

| 

a 

ft 

"•S 

a 

ft 

o  > 

£& 

Pi 

« 

,£] 

PQ 

-p. 
-<  So 

PJ 

pCj 

tt 

H^ 

p? 

PQ 

£  a 

t"1  CD 

P5 

PQ 

§-| 

« 

PQ 

£| 

PS 

pC] 

PQ 

9912 

1200 

3955 

251 

3.12 

4152 

264 

3.82 

4470 

285 

4.62 

4950 

315 

5.42 

5230 

333 

6.36 

5750 

366 

8.17 

10738 

1300 

4050 

258 

3.40 

4380 

278 

4.16 

4550 

290 

4.96 

5024 

320 

5.83 

5295 

337 

6.72 

5820 

370 

8.60 

11564 

1400 

4143 

263 

3.74 

4465 

285 

4.54 

4700 

299 

5.38 

5105 

325 

6.25 

5350 

340 

7.22 

5900 

375 

9.13 

12390 

1500 

4250 

270 

4.11 

4570 

291 

4.93 

4850 

308 

5.80 

5180 

329 

6.72 

5450 

347 

7.67 

5950 

379 

9.72 

13216 

1600 

4325 

275 

4.50 

4652 

297 

5.38 

4950 

315 

6.27 

5245 

334 

7.18 

5550 

353 

8.20 

6025 

383 

10.26 

14042 

1700 

4437 

282 

4.92 

4750 

302 

5.90 

5040 

321 

6.79 

5330 

339 

7.75 

5625 

358 

8.76 

6100 

388 

10.85 

14868 

1800 

4527 

288 

5.38 

4846 

308 

6.36 

5110 

325 

7.29 

5410 

344 

8.36 

5700 

363 

9.37 

6195 

394 

11.55 

15694 

1900 

4613 

294 

5.86 

4945 

314 

6.85 

5230 

333 

7.87 

5520 

351 

8.97 

5780 

368 

10.02 

6265 

398 

12.22 

16520 

2000 

4743 

301 

6.41 

5075 

323 

7.44 

5325 

339 

8.50 

5620 

357 

9.63 

5860 

373 

10.73 

6365 

405 

12.97 

17346 

2100 

4850 

308 

6.95 

5145 

328 

8.05 

5440 

346 

9.17 

5724 

364 

10.32 

5955 

379 

11.44 

6475 

412 

13.80 

18172 

2200 

4970 

316 

7.58 

5256 

334 

8.68 

5550 

354 

9.85 

5790 

368 

11.03 

6050 

385 

12.18 

6550 

417 

14.65 

18998 

2300 

5090 

324 

8.60 

5370 

342 

9.42 

5630 

358 

10.55 

5900 

375 

11.82 

6150 

391 

13.00 

6610 

421 

15.54 

19824 

2400 

5210 

332 

8.97 

5480 

349 

10.15 

5750 

366 

11.32 

6025 

383 

12.64 

6270 

399 

13.86 

6700 

426 

16.51 

20650 

2500 

5340 

340 

9.75 

5610 

357 

10.90 

5850 

372 

12.18 

6100 

388 

13.46 

6343 

403 

14.80 

6800 

432 

17.48 

21476 

2600 

5485 

349 

10.55 

5740 

366 

11.80 

5980 

381 

13.06 

6200 

394 

14.37 

6460 

411 

15.80 

6880 

438 

18.50 

23128 

2800 

5710 

364 

12.43 

5960 

379 

13.62 

6230 

396 

15.03 

6460 

411 

16.42 

6650 

423 

17.85 

7090 

451 

20.73 

24780 

3000 

5970 

380 

14.28 

6200 

395 

15.68 

6460 

411 

17.20 

6675 

425 

18.63 

6900 

439 

20.15 

7295 

464 

28.15 

26432 

3200 

6230 

396 

16.43 

6475 

412 

18.00 

6730 

428 

19.60 

6920 

441 

21.07 

7135 

448 

22.67 

7530 

478 

25.73 

28084 

3400 

6580 

418 

19.00 

6740 

429 

20.60 

6960 

443 

22.25 

7150 

455 

23.88 

7355 

469 

25.40 

7750 

493 

28.70 

29736 

3600 

6815 

433 

21.65 

7020 

447 

23.35 

7200 

458 

25.13 

7440 

473 

26.75 

7600 

484 

28.60 

8020 

511 

31.90 

31388 

3800 

7105 

452 

24.70 

7350 

468 

26.60 

7475 

476 

28.30 

7660 

488 

30.10 

7840 

499 

31.80 

8220 

523 

35.55 

308 


HEATING  AND  VENTILATION 


CAPACITY  TABLE 

TABLE  IX. — No.  110  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


S.  P.  K" 

S.  P.  H" 

S.  P.  H" 

S.  P.  W' 

S.  P.  K" 

S.  P.  H" 

Vr>1 

•3-s 

V  Ol- 

ume 

+_>  & 

§> 

"8 

a 

ft 

"8 

a 

ft 

1 

a 

ft 

"8 

a 

ft 

8 

a 

ft 

1 

a 

ft 

a£ 

a 

M 

a£ 

ft 

,£j 

a£ 

ft 

A 

a£ 

A 

JS, 

as 

P. 

M 

aS 

A 

JS 

£  a 

f  OS 

PJ 

« 

H  m 

PS 

ffl 

£  ft 

M  tn 

PS 

PQ 

Hft 

rt 

« 

Hft 

p4 

M 

C  a 

T^  CO 

« 

PQ 

9760 

1000 

2366 

137 

.945 

2690 

156 

1.26 

2940 

170 

1.58 

3175 

184 

1.92 

3400 

197 

2.26 

3610 

209 

2.6 

10736 

1100 

2490 

144 

1.11 

2780 

161 

1.46 

3040 

176 

1.81 

3267 

190 

2.17 

3480 

202 

2.53 

3670 

212 

2.9 

11712 

1200 

2600 

151 

1.32 

2925 

169 

1.69 

3125 

181 

2.05 

3360 

195 

2.44 

3575 

207 

2.84 

3763 

218 

3.2 

12688 

1300 

2736 

157 

1.56 

3000 

174 

1.93 

3237 

187 

2.32 

3475 

201 

2.74 

3675 

213 

3.16 

3865 

224 

3.5 

13664 

1400 

2846 

165 

1.81 

3107 

180 

2.21 

3310 

192 

2.61 

3573 

207 

3.06 

3750 

217 

3.50 

3965 

230 

3.9 

14640 

1500 

2987 

173 

2.12 

3226 

187 

2.54 

3460 

200 

2.97 

3650 

211 

3.43 

3860 

224 

3.88 

4060 

235 

4.3 

15616 

1600 

3130 

183 

2.44 

3350 

194 

2.89 

3565 

207 

3.34 

3765 

218 

3.81 

3960 

229 

4.29 

4160 

241 

4.8 

16592 

1700 

3270 

189 

2.79 

3475 

201 

3.27 

3680 

213 

3.74 

3885 

225 

4.24 

4055 

235 

4.76 

4250 

246 

5.2 

17568 

1800 

3410 

197 

3.25 

3607 

209 

3.71 

3810 

221 

4.22 

4010 

232 

4.72 

4180 

242 

5.36 

4350 

252 

5.8 

18544 

1900 

3546 

206 

3.63 

3730 

216 

4.18 

3935 

228 

4.68 

4120 

239 

5.23 

4320 

250 

5.79 

4455 

258 

6.3 

19520 

2000 

3700 

214 

4.11 

3860 

224 

4.68 

4050 

235 

5.22 

4255 

245 

5.82 

4423 

257 

6.39 

4580 

265 

6.9 

20496 

2100 

3850 

223 

4.63 

4000 

232 

5.24 

4210 

244 

5.77 

4350 

252 

6.42 

4535 

262 

7.02 

4680 

271 

7.6 

21472 

2200 

4000 

232 

5.18 

4168 

242 

5.87 

4320 

251 

6.46 

4500 

261 

7.08 

4670 

271 

7.72 

4800 

278 

8.3 

22448 

2300 

4323 

251 

6.50 

4450 

258 

7.10 

4628 

268 

7.76 

4770 

277 

8.45 

4930 

286 

9.1 

23424 

2400 

4460 

258 

7.02 

4620 

268 

7.88 

4740 

275 

8.55 

4920 

285 

9.24 

5045 

292 

9.9 

24400 

2500 

4600 

266 

7.93 

4720 

273 

8.63 

4880 

283 

9.37 

5036 

292 

10.05 

5170 

300 

10.7 

25376 

2600 

4910 

284 

9.55 

5000 

290 

10.25 

5180 

300 

11.00 

5325 

308 

11.7 

27328 

2800 

5180 

300 

11.3 

5280 

306 

12.17 

5435 

315 

12.88 

5510 

319 

13.8 

29280 

3000 

5485 

317 

13.4 

5610 

325 

14.34 

5650 

327 

15.08 

5840 

338 

16.0 

S.  P.  1" 

S.  P.  IJtf" 

S.  P.  W 

S.  P.  l%" 

S.  P.  2" 

S.  P.  2H" 

Vnl 

fl) 

V  Ol~ 

ume 

3    . 
£"» 

13 

a 

ft 

T3 

a 

ft 

iM 

ft 

"8 

a 

ft 

"S 

a 

ft 

"8 

a 

ft 

O  > 

0.1 

a 

^ 

aS 

P. 

^ 

ftS    ft 

,4 

ft£ 

ft 

^3 

o,£ 

ft 

A 

a£ 

a 

M 

H! 

tf 

ffl 

Ha 

p4 

« 

?l 

'« 

PQ 

H& 

P? 

PQ 

Ha 

tf 

PQ 

£  ft 

tr1  on 

p4 

PQ 

11712 

1200 

3955 

229 

3.69 

4152 

241 

4.52 

4470 

259 

5.47 

4950 

287 

6.40 

5230 

303 

7.45 

5750 

333 

9.6 

12688 

1300 

4050 

235 

4.02 

4380 

254 

4.92 

4550 

264 

5.87 

5024 

291 

6.88 

5295 

306 

7.95 

5820 

337 

10.1 

13664 

1400 

4143 

240 

4.42 

4465 

259 

5.37 

4700 

272 

6.36 

5105 

296 

7.38 

5350 

310 

8.53 

5900 

342 

10.7 

14640 

1500 

4250 

246 

4.85 

4570 

265 

5.83 

4850 

281 

6.85 

5180 

300 

7.93 

5450 

316 

9.06 

5950 

345 

11.4 

15616 

1600 

4325 

250 

5.32 

4652 

270 

6.37 

4950 

287 

7.40 

5245 

303 

8.50 

5550 

322 

9.69 

6025 

349 

12.1 

16592 

1700 

4437 

257 

5.81 

4750 

275 

6.97 

5040 

292 

8.02 

5330 

309 

9.17 

5625 

326 

10.34 

6100 

353 

12.8 

17568 

1800 

4527 

262 

6.35 

4846 

280 

7.50 

5110 

296 

8.62 

5410 

313 

9.86 

5700 

330 

11.07 

6195 

358 

13.6 

18544 

1900 

4613 

267 

6.92 

4945 

286 

8.10 

5230 

303 

9.30 

5520 

320 

10.58 

5780 

335 

11.84 

6265 

363 

14.4 

19520 

2000 

4743 

274 

7.57 

5075 

294 

8.80 

5325 

309 

10.03 

5620 

325 

11.37 

5860 

340 

12.68 

6365 

369 

15.3 

20496 

2100 

4850 

281 

8.22 

5145 

298 

9.52 

5440 

315 

10.83 

5724 

332 

12.20 

5955 

345 

13.52 

6475 

375 

16.3 

21472 

2200 

4970 

288 

8.96 

5256 

305 

10.24 

5550 

322 

11.63 

5790 

335 

13.02 

6050 

350 

14.40 

6550 

379 

17.3 

22448 

2300 

5090 

295 

10.15 

5370 

311 

11.11 

5630 

326 

12.48 

5900 

342 

13.96 

6150 

356 

15.37 

6610 

383 

18.3 

23424 

2400 

5210 

302 

10.62 

5480 

312 

11.99 

5750 

333 

13.39 

6025 

349 

14.93 

6270 

363 

16.39 

6700 

388 

19.5 

24400 

2500 

5340 

309 

11.52 

5610 

325 

12.88 

5850 

339 

14.38 

6100 

353 

15.90 

6343 

367 

17.50 

6800 

394 

20.6 

25376 

2600 

5485 

318 

12.47 

5740 

332 

13.96 

5980 

346 

15.43 

6200 

359 

16.97 

6460 

375 

18.70 

6880 

399 

21.8 

27328 

2800 

5710 

331 

14.68 

5960 

345 

16.10 

6230 

361 

17.75 

6460 

375 

19.43 

6650 

385 

21.08 

7090 

405 

24.5 

29280 

3000 

5970 

346 

16.87 

6200 

359 

18.55 

6460 

374 

20.39 

6675 

387 

22.00 

6900 

400 

23.80 

7295 

423 

27.3 

31232 

3200 

6230 

361 

19.43 

6475 

375 

21.30 

6730 

390 

23.10 

6920 

401 

24.90 

7135 

413 

26.75 

7530 

437 

30.4 

33184 

3400 

6580 

381 

22.45 

6740 

390 

24.35 

6960 

403 

26.55 

7150 

414 

28.20 

7355 

427 

30.10 

7750 

449 

33.9 

35136 

3600 

6815 

395 

25.55 

7020 

407 

27.60 

7200 

417 

29.70 

7440 

431 

31.60 

7600 

440 

33.75 

8020 

465 

37.7 

37088 

3800 

7105 

412 

29.15 

7350 

426 

31.47 

7475 

433 

33.35 

7660 

444 

35.55 

7840 

454 

37.55 

8220 

476 

42.0 

APPENDIX 


309 


CAPACITY  TABLE 

TABLE  X. — No.  120  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


Vnl 

gj 

s.  P.  K" 

S.  P.  W 

S.  P.  M" 

S.  P.  «" 

s.  P.  H" 

S.  P.  %" 

V  Ol* 

ume 

»—  4 

JN 

"S 

a 

ft 

T3 

S 

ft 

"2 

a 

ft 

"S 

a 

ft 

"8 

a 

ft 

"8 

a 

ft 

o  > 

a£ 

a 

A 

ft£ 

a 

A 

ft£ 

a 

A 

a8 

P. 

A 

&® 

o. 

A 

a£ 

o. 

A 

H& 

tf 

pq 

H  §* 

p4 

H 

^  ft 

M 

M 

H  & 

PS 

ffl 

Ct  a 
r1  m 

PJ 

pq 

3  ft 

p4 

pq 

11950 

1000 

2366 

125 

1.156 

2690 

143 

1.54 

2940 

156 

1.44 

3175 

168 

2.35 

3400 

180 

2.77 

3610 

191 

3.24 

13145 

1100 

2490 

132 

1.36 

2780 

147 

1.79 

3040 

161 

2.21 

3267 

173 

2.66 

3480 

185 

3.11 

3670 

195 

3.59 

14340 

1200 

2600 

138 

1.60 

2925 

155 

2.07 

3125 

166 

2.51 

3360 

178 

2.99 

3575 

189 

3.48 

3763 

200 

3.97 

15535 

1300 

2736 

145 

1.91 

3000 

159 

2.36 

3237 

172 

2.85 

3475 

184 

3.36 

3675 

195 

3.87 

3865 

205 

4.39 

16730 

1400 

2846 

151 

2.23 

3107 

165 

2.71 

3310 

176 

3.20 

3573 

189 

3.75 

3750 

199 

4.29 

3965 

210 

4.85 

17925 

1500 

2987 

158 

2.60 

3226 

171 

3.11 

3460 

184 

3.64 

3650 

194 

4.20 

3860 

205 

4.76 

4060 

215 

5.35 

19120 

1600 

3130 

166 

2.99 

3350 

178 

3.54 

3565 

189 

4.08 

3765 

200 

4.67 

3960 

210 

5.26 

4160 

220 

5.87 

20315 

1700 

3270 

173 

3.42 

3475 

184 

4.02 

3680 

195 

4.61 

3885 

206 

5.19 

4055 

215 

5.88 

4250 

226 

6.48 

21510 

1800 

3410 

181 

3.99 

3607 

191 

4.54 

3810 

202 

5.17 

4010 

213 

5.79 

4180 

222 

6.56 

4350 

231 

7.16 

22705 

1900 

3546 

188 

4.45 

3730 

198 

5.12 

3935 

209 

5.74 

4120 

219 

6.42 

4320 

229 

7.10 

4455 

236 

7.77 

23900 

2000 

3700 

196 

5.04 

3860 

205 

5.74 

1050 

215 

6.40 

4255 

226 

7.14 

4423 

235 

7.83 

4580 

243 

8.54 

25095 

2100 

3850 

204 

5.68 

4000 

212 

6.42 

1210 

223 

7.08 

4350 

231 

7.87 

4535 

241 

8.61 

4680 

248 

9.33 

26290 

2200 

4000 

212 

6.36 

1168 

221 

7.19 

4320 

229 

7.92 

4500 

239 

8.68 

4670 

248 

9.47 

4800 

254 

10.22 

27485 

2300 

4323 

230 

8.08 

4450 

236 

8.70 

4628 

245 

9.51 

4770 

253 

10.35 

4930 

262 

11.15 

28680 

2400 

1460 

237 

8.62 

4620 

245 

9.65 

4740 

251 

10.45 

4920 

261 

11.33 

5045 

268 

12.14 

39375 

2500 

1600 

244 

9.70 

4720 

251 

10.58 

1880 

259 

11.48 

5036 

267 

12.32 

5170 

275 

13.20 

31070 

2600 

4910 

261 

11.70 

5000 

265 

12.55 

5180 

275 

13.48 

5325 

282 

14.35 

33460 

2800 

5180 

275 

13.87 

5280 

280 

14.92 

5435 

288 

15.80 

5510 

292 

16.88 

35850 

3000 

5485 

291 

16.40 

5610 

298 

17.88 

5650 

300 

18.48 

5840 

310 

19.60 

Vnl 

«-> 

S.  P.  1" 

S.  P.  IK" 

S.  P.  IK" 

s.  P.  \H" 

S.  P.  2" 

S.  P.  2H" 

v  01- 
ume 

£      • 

*1 

'S 

a 

ft 

13 

a 

ft 

-0 

a 

ft 

•& 

a 

ft 

T3 

a 

ft 

"8 

a 

a 

0> 

a£ 

ft 

A 

a£ 

& 

A 

a£ 

a 

A 

o,£ 

ft 

A 

ft£ 

a 

A 

a£ 

a 

A 

£  a 

"*  OB 

PJ 

pq 

r~    ft 
C"1    03 

PS 

PQ 

Ct  ft 

t"1    02 

p4 

« 

£  ft 
t-1  oo 

tf 

pq 

£  ft 

tr1  on 

tf 

pq 

H  ft 

rt 

B 

14340 

1200 

3955 

209 

4.52 

4152 

220 

5.52 

4470 

237 

6.69 

4950 

262 

7.83 

5230 

279 

9.12 

5750 

305 

11.73 

15535 

1300 

4050 

215 

4.92 

4380 

232 

6.02 

1550 

242 

7.18 

5024 

267 

8.43 

5295 

281 

9.75 

5820 

309 

12.4 

16730 

1400 

4143 

220 

5.40 

4465 

237 

6.57 

4700 

249 

7.80 

5105 

271 

9.04 

5350 

284 

10.44 

5900 

313 

13.2 

17925 

1500 

4250 

226 

5.95 

4570 

243 

7.15 

4850 

257 

8.40 

5180 

275 

9.73 

5450 

289 

11.10 

5950 

316 

14.0 

19120 

1600 

3325 

229 

6.50 

4652 

247 

7.80 

4950 

263 

9.08 

5245 

278 

10.40 

5550 

294 

11.87 

6025 

320 

14.8 

20315 

1700 

4437 

235 

7.12 

4750 

252 

8.55 

5040 

268 

9.84 

5330 

283 

11.22 

5625 

298 

12.1 

6100 

324 

15.7 

21510 

1800 

4527 

240 

7.78 

4846 

257 

9.20 

5110 

271 

10.56 

5410 

287 

12.10 

5700 

302 

13.6 

6195 

328 

16.7 

22705 

1900 

4613 

245 

8.48 

4945 

262 

9.92 

5230 

277 

11.33 

5520 

293 

12.9 

5780 

307 

14.5 

6266 

333 

17.7 

23900 

2000 

4743 

251 

9.27 

5075 

269 

10.77 

5325 

283 

12.3 

5620 

298 

13.9 

5860 

311 

15.5 

6365 

338 

18.7 

25095 

2100 

4850 

257 

10.07 

5145 

273 

11.67 

5440 

289 

13.2 

5724 

304 

14.9 

5955 

316 

16.5 

6475 

344 

20.0 

26290 

2200 

4970 

264 

10.97 

5256 

279 

12.56 

5550 

294 

14.2 

5790 

307 

15.9 

6050 

321 

17.6 

6550 

348 

21.2 

27485 

2300 

5090 

27012.45 

5370 

285 

13.60 

5630 

299 

15.3 

5900 

313 

17.1 

6150 

326 

18.8 

6610 

351 

22.5 

28680 

2400 

5210 

27612.98 

5480 

292 

14.70 

5750 

305 

16.4 

6025 

320 

18.3 

6270 

333 

20.1 

6700 

356 

23.9 

29875 

2500 

5340 

28314.12 

5610 

298 

15.78 

5850 

310 

17.6 

6100 

324 

19.5 

6343 

336 

21.5 

6800 

361 

25.3 

31070 

2600 

5485 

29115.27 

5740 

304 

17.10 

5980 

317 

18.9 

6200 

329 

20.8 

6460 

343 

22.9 

6880 

365 

26.7 

33460 

2800 

5710 

30318.00 

5960 

316 

19.73 

6230 

331 

21.7 

6460 

343 

23.8 

6650 

353 

25.8 

7090 

376 

30.0 

35850 

3000 

5970 

31720.68 

6200 

329 

22.70 

6460 

343 

24.9 

6675 

354 

26.9 

6900 

366 

29.2 

7295 

387 

33.5 

38240 

3200 

6230 

330,23.80 

6475 

344 

26.10 

6730 

357 

28.3 

6920 

367 

30.5 

7135 

378 

32.8 

7530 

399 

37.2 

40630 

3400 

6580 

34927.50 

6740 

357 

29.85 

6960 

320 

32.1 

7150 

379 

34.6 

7355 

391 

36.8 

7750 

411 

41.7 

43020 

3600 

6815 

36231.30 

7000 

372 

33.80 

7200 

382 

36.4 

7440 

394 

38.7 

7600 

404 

41.4 

8020 

426 

46.2 

45410 

3800 

7105 

37735.80 

7350 

390 

38.50 

7475 

397 

41.0 

7660 

407 

43.6 

7840 

417 

46.0 

8220 

436 

51.4 

310 


HEATING  AND  VENTILATION 


CAPACITY  TABLE 

TABLE  XI. — No.  130  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


Vol- 

g 

S.  P.  K" 

S.  P.  %" 

S.  P.  M" 

S.  P.  H" 

S.  P.  H" 

S.  P.  H" 

ume 

»f 

-0 

a 

ft 

TJ 

a 

ft 

i 

a 

ft 

1 

a 

ft 

I 

a 

ft 

4 

S 

ft 

3 

CX  o 

o. 

ft  0) 

& 

& 

ft 

ft$ 

P. 

9-1 

ft 

M 

£  ft 

fcH  oo 

05 

PQ 

•*  oo 

P5 

PQ 

H! 

05 

PQ 

H   00 

05 

pq 

2  ft 

IT1  to 

05 

PQ 

£  & 

05 

PQ 

14050 

1000 

2366 

116 

1.360 

2690 

132 

1.820 

2940 

144 

2.280 

3175 

156 

2.765 

3400 

166 

3.262 

3610 

177 

3.810 

15455 

1100 

2490 

122 

1.602 

2780 

136 

2.101 

3040 

149 

2.607 

3267 

160 

3.128 

3480 

171 

3.658 

3670 

180 

4.218 

16860 

1200 

2600 

127 

1.909 

2925 

143 

2.433 

3125 

153 

2.952 

3360 

165 

3.516 

3575 

175 

4.091 

3763 

184 

4.668 

18265 

1300 

2736 

134 

2.250 

3060 

147 

2.790 

3237 

157 

3.351 

3475 

170 

3.950 

3675 

180 

4.555 

3865 

189 

5.162 

19670 

1400 

2846 

139 

2.620 

3107 

152 

3.190 

3310 

162 

3.771 

3573 

175 

4.414 

3750 

184 

5.050 

3965 

194 

5.710 

21075 

1500 

2987 

146 

3.060 

3226 

158 

3.660 

3460 

170 

4.290 

3650 

179 

4.937 

3860 

189 

5.595 

4060 

199 

6.290 

22480 

1600 

3130 

154 

3.515 

3350 

164 

4.168 

3565 

175 

4.807 

3765 

185 

5.500 

3960 

193 

6.190 

1160 

204 

6.918 

23885 

1700 

3270 

160 

4.027 

3475 

170 

4.717 

3680 

180 

5.408 

3885 

190 

6.102 

4055 

197 

6.868 

1250 

208 

7.620 

25290 

1800 

3410 

167 

4.690 

3607 

177 

5.345 

3810 

187 

6.078 

4010 

196 

6.800 

1180 

205 

7.715 

4350 

213 

8.423 

26695 

1900 

3546 

174 

5.230 

3730 

183 

6.020 

3935 

193 

6.752 

4120 

202 

7.550 

1320 

212 

8.350 

1455 

218 

9.147 

28100 

2000 

3700 

181 

5.935 

3860 

189 

6.250 

4050 

198 

7.540 

4255 

209 

8.400 

1423 

217 

9.210 

1580 

225 

10.04 

29505 

2100 

3850 

189 

6.678 

4000 

196 

7.550 

4210 

206 

8.320 

4350 

213 

9.253 

1535 

222 

10.120 

1680 

229 

10.97 

30910 

2200 

4000 

196 

7.475 

4168 

204 

8.452 

1320 

212 

9.300 

1500 

221 

10.20 

4670 

229 

11.120 

1800 

235 

12.02 

32315 

2300 

4323 

212 

9.230 

1450 

218 

10.23 

1628 

227 

11.18 

4770 

234 

12.170 

1930 

242 

13.12 

33720 

2400 

1460 

219 

10.130 

1620 

226 

11.34 

1740 

232 

12.30 

4920 

241 

13.30 

5045 

247 

14.26 

35125 

2500 

4600 

226 

11.40 

4720 

231 

12.43 

4880 

239 

13.48 

5036 

247 

14.48 

5170 

253 

15.49 

36530 

2600 

1910 

241 

13.75 

5000 

245 

14.76 

5180 

254 

15.85 

5325 

261 

16.87 

39340 

2800 

5180 

254 

16.29 

5280 

259 

17.53 

5435 

266 

18.60 

5410 

270 

19.87 

42150 

3000 

5485 

269 

19.30 

5610 

275 

20.66 

5650 

277 

21.74 

5840 

286 

23.06 

S.  P.  1" 

S.  P.  IK" 

S.  P.  1H" 

S.  P.  IX" 

S.  P.  2" 

S.  P.  2M" 

Vnl 

§ 

v  oi- 
uine 

73 

31 

»i 

a 
ft 

ft 
M 

*1 

a 
P. 

ft 
M 

s! 

a 
ft 

ft 
ft 

A 

a 

4 

ft 

,£5 

91 

a 

ft 

ft 

<Cj 

ft| 

a 

ft 

ft 

,c 

'Hi  ft 
r*  oo 

05 

PQ 

r«8 

rt 

to 

£  ft 

r*  on 

05 

PQ 

£  ft 

f    00 

05 

ffl 

£   ft 

IT1    OQ 

05 

PQ 

H& 

05 

PQ 

16860 

1200 

3955 

194 

5.303 

4152 

204 

6.501 

4470 

219 

7.875 

4950 

243 

9.32 

5230 

256 

10.73 

5750 

282 

13.91 

18265 

1300 

4050 

198 

5.790 

4380 

215 

7.085 

4550 

223 

8.351 

5024 

246 

9.93 

5295 

259 

11.46 

5820 

285 

14.63 

19670 

1400 

4143 

203 

6.355 

4465 

219 

7.337 

4700 

231 

9.160 

5105 

250 

10.63 

5350 

262 

12.28 

5900 

289 

15.53 

21075 

1500 

4250 

208 

7.000 

4570 

224 

8.400 

4850 

238 

9.870 

5180 

254 

11.43 

5450 

267 

13.05 

5950 

29116.50 

22480 

1600 

4325 

212 

7.650 

4652 

229 

9.170 

4950 

243 

10.67 

5245 

257 

12.23 

5550 

272 

13.45 

6025 

29517.49 

23855 

1700 

4437 

217 

8.375 

4750 

233 

10.04 

5040 

247 

11.56 

5330 

262 

13.20 

5625 

276 

14.90 

6100 

299 

18.48 

25290 

1800 

4527 

222 

9.150 

4846 

238 

10.80 

5110 

251 

12.41 

5410 

265 

14.25 

5700 

27915.94 

6195 

303 

19.65 

26695 

1900 

4613 

226 

9.980 

4945 

243 

11.67 

5230 

256 

13.38 

5520 

270 

15.27 

5780 

28317.05 

6265 

307 

20.83 

28100 

2000 

4743 

232 

10.90 

5075 

249 

12.67 

5325 

261 

14.46 

5620 

275 

16.40 

5860 

287 

19.27 

6365 

312 

22.10 

29505 

2100 

4850 

238 

11.83 

5145 

252 

13.70 

5440 

267 

15.59 

5724 

280 

17.88 

5955 

292 

19.50 

6425 

317 

23.50 

30910 

2200 

4970 

243 

12.90 

5256 

257 

14.78 

5550 

272 

16.77 

5790 

284 

18.78 

6050 

29620.73 

6550 

321 

24.94 

32315 

2300 

5090 

249 

14.63 

5370 

263 

16.00 

5630 

276 

17.99 

5900 

289 

20.10 

6150 

30122.13 

6610 

324 

26.46 

33720 

2400 

5210 

255 

15.27 

5480 

269 

17.27 

5750 

282 

19.29 

6025 

295 

21.50 

6270 

307 

23.60 

6700 

329 

28.10 

35125 

2500 

5340 

262 

16.59 

5610 

275 

18.55 

5850 

287 

20.73 

6100 

299 

22.90 

6343 

311 

25.23 

6800 

333 

29.73 

36530 

2600 

5485 

269 

17.96 

5740 

281 

20.12 

5980 

293 

22.24 

6200 

304 

24.38 

6460 

316 

26.90 

6880 

339 

31.50 

39340 

2800 

5710 

280 

21.14 

5960 

292 

23.20 

6230 

305 

25.60 

6460 

317 

28.00 

6650 

326 

30.35 

7090 

342 

35.30 

42150 

3000 

5970 

292 

24.32 

6200 

303 

26.72 

6460 

317 

29.30 

6675 

327 

31.70 

6900 

338 

34.30 

7295 

357 

39.40 

44960 

3200 

6230 

305 

28.00 

6475 

317 

30.63 

6730 

330 

33.32 

6920 

339 

35.90 

7135 

34938.60 

7593 

369 

43.80 

47770 

3400 

6580 

322 

32.35 

6740 

330 

35.08 

6960 

341 

37.80 

7150 

351 

40.70 

7355 

36143.30 

7750 

38049.00 

50580 

3600 

6815 

335 

36.82 

7020 

344 

39.80 

7200 

353 

42.80 

7440 

365 

45.60 

7600 

373148.70 

8020 

39554.30 

53390 

3800 

7105 

349 

42.02 

7350 

360 

45.37 

7475 

367 

48.20 

7660 

375 

51.20 

7840 

384 

54.20 

8220 

40360.50 

APPENDIX 


311 


CAPACITY  TABLE 
TABLE  XII. — No.  140  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


Vr>l 

S.  P.  K" 

S.  P.  H" 

S.  P.  K" 

S.  P.  W 

S.  P.  %" 

S.  P.  W 

V  Ol™ 

ume 

9 

3'oi 

,-C 

6 

a 

"2 

a 

ft 

T3 

a 

ft 

T3 

a 

ft 

1 

a 

ft 

1 

S 

i 

ft 

O  > 

a$ 

a 

,4 

a£ 

p. 

JA 

a£ 

ft 

,C| 

ft£ 

Q. 

43 

ftS 

P 

43 

ftS 

ft 

ja 

H   £ 

P5 

pq 

Ha 

tf 

pq 

u,  ft 
tr"  oo 

rt 

« 

H& 

p4 

« 

Ha 

« 

pq 

^a 

PS 

CQ 

16000 

1000 

2366 

108 

1.550 

2690 

123 

2.072 

2940 

134 

2.596 

3175 

145 

3.150 

3400 

155 

3.715 

3610 

164 

4.337 

17600 

1100 

2490 

113 

1.825 

2780 

127 

2.392 

3040 

138 

2.967 

3267 

149 

3.560 

3480 

158 

4.160 

3670 

167 

4.800 

19200 

1200 

2600 

118 

2.172 

2925 

133 

2.770 

3125 

142 

3.360 

3360 

153 

4.000 

3575 

163 

4.655 

3763 

171 

5.318 

20800 

1300 

2736 

124 

2.560 

3000 

137 

3.175 

3237 

147 

3.817 

3475 

158 

4.500 

3675 

167 

5.187 

3865 

176 

58.80 

22400 

1400 

2846 

129 

2.980 

3107 

141 

3.630 

3310 

151 

4.299 

3573 

163 

5.025 

3750 

171 

5.750 

3965 

180 

65.10 

24000 

1500 

2987 

136 

3.482 

3226 

147 

4.168 

3460 

157 

4.885 

3650 

166 

5.620 

3860 

176 

6.370 

4060 

185 

7.160 

25600 

1600 

3130 

142 

4.000 

3350 

153 

4.747 

3565 

162 

5.475 

3765 

171 

6.255 

3960 

180 

7.045 

4160 

189 

7.870 

27200 

1700 

3270 

149 

4.585 

3475 

158 

5.368 

3680 

168 

6.155 

3885 

177 

6.950 

4055 

184 

7.820 

4250 

193 

86.70 

28800 

1800 

3410 

155 

5.340 

3607 

164 

6.087 

3810 

173 

6.920 

4010 

183 

7.750 

4180 

190 

8.787 

4350 

198 

9.590 

30400 

1900 

3546 

161 

5.950 

3730 

170 

6.850 

3935 

179 

7.699 

4120 

187 

8.600 

4320 

197 

9.510 

4455 

203 

10.4 

32000 

2000 

3700 

168 

6.750 

3860 

176 

7.690 

4050 

184 

8.580 

4255 

194 

9.560 

4423 

201 

10.5 

4580 

209 

11.4 

33600 

2100 

3850 

175 

7.600 

4000 

182 

8.600 

4210 

191 

9.475 

4350 

198 

10.5 

4535 

206 

11.5 

4680 

213 

12.5 

35200 

2200 

4000 

182 

8.520 

4168 

189 

9.625 

4320 

197 

10.6 

4500 

205 

11.6 

4670 

213 

12.7 

4800 

219 

13.7 

36800 

2300 

4323 

197 

10.6 

4450 

20311.6 

4628 

210 

12.7 

4770 

217 

13.9 

4930 

224 

15.0 

38400 

2400 

4460 

203 

11.5 

4620 

21012.9 

4740 

216 

14.0 

4920 

224 

15.2 

5045 

229 

16.24 

40000 

2500 

4600 

209 

13.0 

4720 

21514.2 

4880 

222 

15.3 

5036 

229 

16.49 

5170 

235 

17.62 

41600 

2600 

4910 

22315.6 

5000 

237 

16.80 

5180 

236 

18.05 

5325 

242 

19.20 

44800 

2800 

5180 

23618.55 

5280 

240 

19.98 

5435 

247 

21.18 

5510 

251 

22.62 

48000 

3000 

5485 

24921.96 

5610 

255 

23.53 

5650 

257 

24.76 

5840 

226 

26.25 

Vnl 

•4J 

S.  P.  1" 

S.  P.  IK" 

S.  P.  IK" 

S.  P.  IK" 

S.  P.  2" 

S.  P.  2K" 

V  Ol~ 

ume 

It 

ftl 

a 
a 

a 

43 

»1 

a 
& 

ft 

43 

-i 

a 

a 

ft 

ftl 

a 
a 

ft 

43 

»1 

a 

a 

4 

»l 

a 
a 

a 

^  « 

« 

pq 

H& 

P5 

pq 

—  i  a 

on 

tf 

pq 

-*  x 

p4 

pq 

H    ^* 

PS 

pq 

^_.    Q 

tr1  co 

« 

pq 

19200 

1200 

3955 

180 

6.045 

4152 

189 

7.400 

4470 

203 

8.965 

4950 

225 

10.5 

5230 

236 

12.2 

5750 

262 

15.8 

20300 

1300 

4050 

184 

6.595 

4380 

199 

8.070 

4550 

207 

9.637 

5024 

228 

11.3 

5295 

241 

13.0 

5820 

265 

16.64 

22400 

1400 

4143 

188 

7.247 

4465 

203 

8.808 

4700 

212 

10.4 

5105 

232 

12.1 

5350 

243 

14.0 

5900 

263 

17.68 

24000 

1500 

4250 

193 

7.957 

4570 

208 

9.560 

4850 

221 

11.2 

5180 

236 

13.0 

5450 

248 

14.9 

5950 

271 

18.80 

25600 

1600 

4325 

197 

8.710 

4652 

212 

10.4 

4950 

225 

12.1 

5245 

239 

13.9 

5550 

252 

15.9 

6025 

274 

19.90 

27200 

1700 

4437 

201 

9.545 

4750 

216 

11.4 

5040 

229 

13.2 

5330 

243 

15.0 

5625 

256 

16.98 

6100 

277 

21.00 

28800 

1800 

4527 

206 

10.4 

4846 

221 

12.3 

5110 

232 

14.2 

5410 

246 

16.20 

5700 

259 

18.16 

6195 

282 

22.35 

30400 

1900 

4613 

210 

11.4 

4945 

225 

13.3 

5230 

238 

15.3 

5520 

251 

17.37 

5780 

263 

19.43 

6265 

285 

23.68 

32000 

2000 

4743 

21512.4 

5075 

231 

14.4 

5325 

242 

16.45 

5620 

255 

18.65 

5860 

267 

20.80 

6365 

289 

25.10 

33600 

2100 

4850 

221 

13.5 

5145 

234 

15.6 

5440 

247 

17.73 

5724 

260 

20.00 

5955 

271 

22.18 

6475 

294 

26.80 

35200 

2200 

4970 

226 

14.7 

5256 

239 

16.82 

5550 

252 

19.10 

5790 

264 

21.38 

6050 

275 

23.61 

6550 

298 

28.40 

36800 

2300 

5090 

23l|l6.67 

5370 

244 

18.21 

5630 

256 

20.47 

5900 

268 

22.90 

6150 

280 

25.20 

6610 

301 

30.20 

38400 

2400 

5210 

23717.39 

5480 

249 

19.67 

5750 

261 

22.00 

6025 

274 

24.46 

6270 

285 

26.90 

6700 

305 

32.00 

40000 

2500 

5340 

24318.89 

5610 

255 

21.12 

5850 

266 

23.60 

6100 

277 

26.10 

6343 

289 

28.72 

6800 

309 

33.80 

41600 

2600 

5485 

249,20.46 

5743 

261 

22.90 

5980 

272 

25.35 

6200 

282 

27.85 

6460 

293 

30.65 

6880 

313 

35.80 

44800 

2800 

5710 

26024.08 

5960 

271 

26.41 

6230 

283 

29.15 

6460 

293 

31.85 

6650 

303 

34.60 

7090 

322 

40.10 

48000 

3000 

5970 

27227.70 

6200 

282 

30.40 

6460 

294 

33.36 

6675 

304 

36.10 

6900 

314 

39.08 

7295 

332 

44.90 

51200 

3200 

6230 

283!31.90 

6475 

294 

34.90 

6730 

306 

37.95 

6920 

315 

40.80 

7135 

324 

43.90 

7530 

343 

50.00 

54400 

3400 

6580 

299:36.80 

6740 

307 

39.92 

6960 

316 

43.07 

7150 

325 

46.25 

7355 

335 

49.30 

7750 

353 

55.70 

57600 

3600 

6815 

31041.92 

7020 

319 

45.30 

7200 

327 

48.07 

7440 

339 

51.99 

7600 

346 

55.38 

8020 

365 

61.80 

60800 

3800 

7105 

323 

47.90 

7350 

334 

51.60 

7475 

340 

54.92 

7660 

349 

58.37 

7840 

357 

61.60 

8220 

374 

69.00 

312 


HEATING  AND  VENTILATION 


CAPACITY  TABLE 
TABLE  XIII. — No.  160  SINGLE  INLET  STEEL  PLATE  FAN — TYPE  S 


S.  P.  K" 

s.  P.  H" 

S.  P.  K" 

S.  P.  H" 

S.  P.  %" 

S.  P.  %" 

Vol- 

«J 

ume 

3-3 

•fi 

a 

ft 

•fi 

a 

d 

-0 

3 

d 

•B 

a 

ft 

- 

a 

ft 

•0 

a 

ft 

O> 

a2> 

d 

jg 

8*1 

ft 

M 

.S1^ 

ft 

A 

at> 

d 

A 

Di  o 

d 

A 

D*  o) 

ft 

A 

H& 

« 

PQ 

H& 

PS 

pq 

?  & 

PS 

« 

Ha 

p4 

« 

H& 

« 

m 

r*S 

PS 

pq 

20250 

1000 

2366 

94 

1.957 

2690 

107 

2.615 

2940 

117 

3.28 

3175 

127 

3.98 

3400 

135 

4.69 

3610 

144 

5.48 

22275 

1100 

2490 

99 

2.31 

2780 

111 

3.025 

3040 

121 

3.75 

3267 

130 

4.5 

3480 

139 

5.25 

3670 

146 

6.08 

24300 

1200 

2600 

104 

2.75 

2925 

116 

3.505 

3125 

125 

4.25 

3360 

134 

5.06 

3575 

142 

5.89 

3763 

150 

6.72 

26325 

1300 

2736 

109 

3.23 

3060 

119 

4.01 

3237 

129 

4.82 

3475 

138 

5.68 

3675 

146 

6.55 

3865 

154 

7.44 

28350 

1400 

2846 

113 

3.77 

3107 

124 

4.59 

3310 

132 

5.43 

3573 

142 

6.35 

3750 

149 

7.26 

3965 

158 

8.2 

30375 

1500 

2987 

119 

4.40 

3226 

128 

5.27 

3460 

137 

6.17 

3650 

145 

7.1 

3860 

154 

8.05 

4060 

162 

9.05 

32400 

1600 

3130 

125 

5.06 

3350 

133 

5.99 

3565 

142 

6.92 

3765 

150 

7.91 

3960 

158 

8.9 

4160 

166 

9.94 

34425 

1700 

3270 

130 

5.78 

3475 

138 

6.79 

3680 

147 

7.77 

3885 

155 

8.78 

4055 

162 

9.88 

4250 

169 

10.93 

36450 

1800 

3410 

136 

6.75 

3607 

144 

7.68 

3810 

152 

8.725 

4010 

160 

9.8 

4180 

167 

10.1 

4350 

173 

12.1 

38475 

1900 

3546 

141 

7.52 

3730 

148 

8.67 

3935 

157 

9.71 

4120 

164 

10.90 

4320 

172 

12.0 

4455 

178 

13.1 

40500 

2000 

3700 

147 

8.54 

3860 

154 

9.71 

4050 

161 

10.83 

4255 

170 

12.1 

4423 

176 

13.2 

4580 

183 

14.4 

42525 

2100 

3850 

153 

9.60 

4000 

159 

10.85 

4210 

167 

11.97 

4350 

173 

13.3 

4535 

181 

14.6 

4680 

187 

15.8 

44550 

2200 

4000 

159 

10.74 

4168 

166 

12.17 

4320 

172 

13.40 

4500 

179 

14.7 

4670 

186 

16.0 

4800 

191 

17.3 

46575 

2300 

4323 

172 

13.44 

4450 

177 

14.70 

4623 

184 

16.1 

4770 

190 

17.5 

4930 

196 

18.9 

48600 

2400 

4460 

178 

14.55 

4620 

184 

16.30 

4740 

189 

17.7 

4920 

196 

19.2 

5045 

201 

20.5 

50625 

2500 

4600 

183 

16.40 

4720 

188 

17.90 

4880 

194 

19.4 

5036 

200 

20.8 

5170 

206 

21.3 

52650 

2600 

4910 

196 

19.80 

5000 

199 

21.3 

5180 

206 

22.8 

5325 

212 

24.3 

56700 

2800 

5180 

206 

23.4 

5280 

210 

25.2 

5435 

216 

56.5 

5410 

220 

28.6 

60750 

3000 

5485 

218 

27.8 

5610 

223 

29.7 

5650 

225 

31.3 

5840 

232 

33.1 

S.  P.  1" 

S.  P.  IK" 

S.  P.  IK" 

S.  P.  1H" 

S.  P.  2" 

S.  P.  2M" 

Vol- 

+j 

ume 

ll 

»i 

a 
p. 

ft 
A 

»1 

a 
d 

ft 
A 

»! 

a 

ft 

ft 

M 

»1 

a 

ft 

ft 

A 

-d 

&i 

a 
d 

ft 
ja 

J 

a 

d 

ft 

A 

H& 

PS 

m 

£  ft 

t*l  DO 

PS 

« 

£  ft 

IT1  m 

p4 

m 

H  & 

P? 

PQ 

H& 

rt 

PQ 

r\  a 

t-i  on 

p4 

pq 

24300 

1200 

3955 

158 

7.64 

4152 

166 

9.35 

4470 

178 

11.3 

4950 

197 

13.3 

5230 

208 

15.4 

5750 

229 

20.0 

26325 

1300 

4050 

161 

8.33 

4380 

175 

10.2 

4550 

182 

12.2 

5024 

200 

14.3 

5295 

211 

16.5 

5820 

232 

21.1 

28350 

1400 

4143 

165 

9.16 

4465 

178 

11.1 

4700 

187 

13.2 

5105 

203 

15.3 

5350 

213 

17.7 

5900 

235 

22.4 

30375 

1500 

4250 

169 

10.04 

4570 

182 

12.1 

4850 

193 

14.2 

5180 

206 

16.4 

5450 

217 

18.8 

5950 

237 

23.7 

32400 

1600 

4325 

172 

11.0 

4652 

186 

13.2 

4950 

197 

15.3 

5245 

209 

17.6 

5550 

222 

20.1 

6025 

240 

25.2 

34425 

1700 

4437 

177 

12.0 

4750 

189 

14.4 

5040 

200 

16.6 

5330 

212 

19.0 

5625 

224 

21.5 

6100 

243 

26.6 

36450 

1800 

4527 

180 

13.1 

4846 

193 

15.6 

5110 

203 

17.9 

5410 

216 

20.4 

5700 

227 

22.9 

6195 

247 

28.3 

38475 

1900 

4613 

184 

14.4 

4945 

197 

16.8 

5230 

208 

19.3 

5520 

220 

21.9 

5780 

230 

24.5 

6265 

249 

29.9 

40500 

2000 

4743 

189 

15.7 

5075 

202 

18.2 

5325 

212 

20.8 

5620 

224 

23.5 

5860 

233 

26.3 

6365 

253 

31.8 

42525 

2100 

4850 

193 

17.0 

5145 

205 

19.7 

5440 

216 

22.5 

5724 

228 

25.3 

5955 

237 

28.1 

6425 

257 

33.8 

44550 

2200 

4970 

198 

18.6 

5256 

209 

21.3 

5550 

221 

24.1 

5790 

230 

27.0 

6050 

241 

29.8 

6550 

261 

35.9 

46575 

2300 

5090 

203 

21.10 

5370 

214 

23.1 

5630 

224 

25.9 

5900 

235 

28.9 

6150 

245 

31.9 

6610 

263 

38.1 

48600 

2400 

5210 

208 

22.0 

5480 

218 

24.9 

5750 

229 

27.8 

6025 

240 

30.9 

6270 

250 

34.0 

6700 

267 

40.4 

50625 

2500 

5310 

213 

23.9 

5610 

224 

26.7 

5850 

233 

29.8 

6100 

243 

33.0 

6343 

252 

36.3 

6800 

271 

42.8 

52656 

2600 

5485 

218 

24.8 

5740 

229 

28.9 

5980 

238 

32.0 

6200 

247 

35.2 

6460 

257 

38.7 

6880 

274 

45.3 

56700 

2800 

5710 

228 

30.4 

5960 

238 

33.4 

6230 

248 

36.8 

8460 

257 

40.3 

6650 

265 

43.7 

7090 

282 

50.8 

60750 

3000 

5970 

238 

35.0 

6200 

247 

38.4 

6460 

257 

42.2 

6675 

265 

45.7 

6900 

274 

49.3 

7295 

290 

56.7 

64800 

3200 

6230 

252 

40.3 

6475 

258 

44.2 

6730 

268 

47.9 

6920 

276 

51.6 

7135 

284 

55.4 

7530 

300 

63.0 

68850 

3400 

6580 

262 

46.5 

6740 

268 

50.5 

6960 

277 

54.4 

7150 

285 

58.5 

7355 

293 

62.4 

7750 

308 

70.3 

72900 

3600 

6815 

272 

53.0 

7000 

279 

57.3 

7200 

287 

61.6 

7440 

296 

65.5 

7600 

303 

70.0 

8020 

320 

78.0 

76950 

3800 

7105 

283 

60.5 

7350 

292 

65.2 

7475 

297 

69.4 

7660 

305 

73.7 

7840 

312 

77.8 

8220 

328 

87.0 

APPENDIX 


313 


STATIC   PRESSURE    TABLES    FOR   NIAGARA    CONOIDAL   FANS1 

TABLE  XIV. — No.  3  NIAGARA  CONOIDAL  FAN  (T?PE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"  s.  P. 

%"S.P. 

W  s.  P. 

H"  S.  P. 

H"S.P. 

K"S.P. 

a 

a 

« 

a 
B 

a 

ft 
rt 

ft 

a 

a 

ft 

tf 

ft 

B 

ft 
tf 

ft 
B 

a 

d 
« 

ft 
W 

a 
o. 
« 

ft 

B 

1000 

1310 

.063 

387 

.09 

483 

.15 

1100 

1440 

.076 

384 

.11 

477 

.16 

1200 

1570 

.090 

387 

.12 

477 

.17 

557 

.23 

1300  • 

1710 

.106 

393 

.14 

470 

.18 

550 

.25 

623 

.32 

1400 

1840 

.122 

400 

.16 

473 

.20 

547 

.26 

617 

.33 

687 

.42 

1500 

1970 

.141 

410 

.18 

477 

.23 

543 

.28 

613 

.35 

680 

.43 

743 

.52 

1600 

2100 

.160 

420 

.21 

480 

.25 

547 

.31 

610 

.37 

673 

.45 

733 

.54 

1700 

2230 

.180 

430 

.24 

490 

.28 

550 

.34 

607 

.40 

670 

.48 

727 

.56 

1800 

2360 

.202 

443 

.28 

500 

.32 

553 

.37 

610 

.43 

667 

.51 

723 

.59 

1900 

2490 

.225 

457 

.31 

510 

.35 

560 

.41 

613 

.47 

667 

.54 

720 

.62 

2000 

2630 

.250 

470 

.35 

520 

.40 

570 

.45 

617 

.52 

667 

.58 

720 

.66 

2100 

2760 

.275 

483 

.39 

530 

.45 

580 

.50 

623 

.56 

670 

.63 

720 

.71 

2200 

2890 

.302 

497 

.44 

543 

.50 

590 

.55 

633 

.61 

677 

.68 

723 

.76 

2300 

3020 

.330 

513 

.49 

557 

.55 

600 

.61 

643 

.67 

683 

.73 

727 

.81 

2400 

3150 

.360 

527 

.55 

570 

.61 

610 

.67 

650 

.73 

690 

.80 

733 

.87 

2500 

3280 

.390 

543 

.60 

583 

.67 

623 

.74 

660 

.80 

700 

.86 

740 

.94 

2600 

3410 

.422 

560 

.67 

597 

.74 

633 

.81 

673 

.88 

710 

.94 

747 

1.02 

2800 

3670 

.489 

590 

.81 

623 

.89 

660 

.96 

693 

1.04 

730 

1.10 

767 

1.17 

3000 

3940 

.560 

623 

.99 

657 

1.04 

687 

1.14 

720 

1.22 

753 

1.29 

780 

1.36 

3200 

4190 

.638 

717 

1.33 

747 

1.42 

780 

1.50 

810 

1.58 

3400 

4460 

.721 

807 

1.75 

833 

1.84 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add  for 
total 
press. 

1"  S.  P. 

1>£"S.P. 

1M"S.P. 

1^"S.P. 

2"  S.  P. 

2H"  S.  P. 

a 
d 
« 

ft 

B 

a 
d 
f4 

ft 

B 

a 

d 

P3 

ft 

B 

a 
d 
« 

ft 
B 

a 

a 
« 

ft 

B 

a 

ft 

tf 

ft 
B 

1300 

1710 

.106 

820 

.58 

1400 

1840 

.122 

810 

.59 

920 

.80 

1027 

1.00 

1500 

1970 

.141 

800 

.62 

913 

.81 

1017 

1.04 

1110 

1.25 

1600 

2100 

.160 

793 

.64 

903 

.84 

1007 

1.06 

1100 

1.29 

1190 

1.53 

1700 

2230 

.180 

783 

.66 

893 

.86 

997 

1.09 

1087 

1.32 

1177 

1.58 

1343 

2.13 

1800 

2360 

.202 

777 

.68 

883 

.89 

983 

1.12 

1077 

1.35 

1167 

1.61 

1330 

2.16 

1900 

2490 

.225 

773 

.71 

877 

.92 

977 

1.14 

1067 

.39 

1157 

.65 

1317 

2.20 

2000 

2630 

.250 

770 

.75 

873 

.95 

970 

1.17 

1057 

.42 

1143 

.68 

1303 

2.24 

2100 

2760 

.275 

770 

.79 

867 

.99 

960 

1.22 

1050 

.46 

1133 

.73 

1297 

2.29 

2200 

2890 

.302 

767 

.84 

863 

1.03 

953 

1.25 

1040 

.50 

1127 

.76 

1287 

2.33 

2300 

3020 

.330 

770 

.89 

860 

1.08 

950 

1.30 

1033 

1.54 

1120 

.81 

1270 

2.38 

2400 

3150 

.360 

773 

.95 

860 

1.13 

947 

1.35 

1027 

.59 

1107 

1.85 

1263 

2.43 

2500 

3280 

.390 

777 

1.03 

860 

1.20 

943 

1.41 

1023 

1.64 

1103 

1.91 

1253 

2.49 

2600 

3410 

.422 

783 

1.09 

863 

1.26 

940  1.47 

1020 

1.70 

1097 

1.96 

12472.54 

2800 

3670 

.489 

800 

1.25 

870 

1.43 

943  1  .  63 

1013 

1.84 

1090 

2.10 

12332.67 

I 

3000 

3940 

.560 

820 

1.44 

883 

1.61 

950  1.81 

1020 

2.02 

1087 

2.25 

1227 

2.82 

3200 

4190 

.638 

8G7 

1.65 

900 

1.83 

9602.02 

1023 

2.23 

1090 

2.47 

1217 

3.00 

3400 

4460 

.721 

863 

1.90 

920 

2.06 

980 

2,26 

1033 

2.47 

1093 

2.69 

1213 

3.21 

3600 

4730 

.810 

883 

2.18 

943 

2.34 

997 

2.53 

1050 

2.76 

1107 

2.96 

1220 

3.48 

3800 

4990 

.900 

1017 

2.84 

1067 

3.04 

1117 

3.28 

1227 

3.76 

4000 

5250 

1.000 

1087 

3.39 

1133 

3.60 

1233 

4.10 

1  From  "Fan  Engineering,"  Buffalo  Forge  Co. 


314 


HEATING  AND  VENTILATION 


TABLE  XV. — No.  3^  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 

min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"  s.  P. 

^"S.P. 

H"  S.  P. 

H"  s.  P. 

W  S.  P. 

K"  S.  P. 

a 

ft 
M 

d. 

w 

a 
a 
tt 

ft 

w 

a 

ft 

« 

ft 

n 

a 

a 

fd 

S 

a 

P. 

M 

wd 

a 

S 

S 

1000 

1790 

.063 

332 

.13 

414 

.20 

1100 

1970 

.076 

329 

.14 

409 

.21 

1200 

2140 

.090 

332 

.16 

409 

.23 

477 

.32 

1300 

2320 

.106 

337 

.18 

403 

.25 

472 

.33 

534 

.43 

1400 

2500 

.122 

343 

.21 

406 

.28 

469 

.36 

529 

.45 

589 

.57 

1500 

2680 

.141 

352 

.24 

409 

.31 

466 

.38 

526 

.48 

583 

.59 

637 

.71 

1600 

2860 

.160 

360 

.28 

412 

.34 

469 

.42 

523 

.51 

577 

.62 

629 

.73 

1700 

3040 

.180 

369 

.32 

422 

.49 

472 

.46 

520 

.55 

574 

.65 

623 

.77 

1800 

3210 

.202 

380 

.37 

429 

.33 

474 

.51 

523 

.59 

572 

.69 

620 

.80 

1900 

3390 

.225 

392 

.42 

437 

.48 

480 

.56 

526 

.64 

572 

.74 

617 

.85 

2000 

3570 

.250 

403 

.48 

446 

.54 

489 

.62 

529 

.70 

572 

.79 

617 

.90 

2100 

3750 

.275 

414 

.53 

454 

.61 

497 

.68 

534 

.76 

574 

.86 

617 

.96 

2200 

3930 

.302 

426 

.59 

466 

.68 

506 

.75 

543 

.83 

580 

.92 

620 

1.03 

2300 

4110 

.330 

440 

.67 

477 

.75 

514 

.83 

552 

.91 

586 

1.00 

623 

1.10 

2400 

4290 

.360 

452 

.74 

489 

.83 

523 

.91 

557 

.99 

592 

1.09 

629 

1.18 

2500 

4470 

.390 

466 

.82 

500 

.91 

534 

1.01 

566 

1.08 

600 

1.17 

634 

1.27 

2600 

4640 

.422 

480 

.91 

512 

1.01 

543 

1.10 

577 

1.19 

609 

1.27 

640 

1.39 

2800 

5000 

.489 

506 

1.10 

534 

1.21 

566 

1.31 

594 

1.41 

626 

1.50 

657 

1.59 

3000 

5360 

.560 

534 

1.35 

563 

1.42 

589 

1.56 

617 

1.65 

646 

1.75 

669 

1.85 

3200 

5720 

.638 

614 

1.81 

640 

1.94 

669 

2.05 

694 

2.16 

3400 

6070 

.721 

692 

2.38 

714 

2.50 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air. 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

1K"S.P. 

IK"  S.  P. 

WS.P. 

2"  S.  P. 

2^"  S.  P. 

a 
d 

M 

S 

a 
D, 

« 

d 
W 

a 
P. 

ej 

S 

a 
a 
« 

ft 

w 

a 
D. 
P! 

ft 

B 

a 
S 

ft 

B 

1300 

2320 

.106 

703 

.78 

1400 

2500 

.122 

694 

.81 

789 

1.08 

880 

1.36 

1500 

2680 

.141 

686 

.84 

783 

1.10 

872 

1.41 

952 

1.70 

1600 

2860 

.160 

680 

.86 

774 

1.15 

863 

1.45 

943 

1.75 

1020 

2.08 

1700 

3040 

.180 

672 

.89 

766 

1.17 

854 

1.48 

932 

1.79 

1009 

2.14 

1151 

2.89 

1800 

3210 

.202 

666 

.93 

757 

1.21 

843 

1.52 

923 

1.84 

1000 

2.19 

1140 

2.94 

1900 

3390 

.225 

663 

.97 

752 

1.25 

837 

1.56 

914 

1.89 

992 

2.24 

1129 

2.99 

2000 

3570 

.250 

660 

1.02 

749 

1.30 

831 

1.59 

906 

1.94 

980 

2.29 

1117 

3.05 

2100 

3750 

.275 

660 

1.08 

743 

1.35 

823 

1.65 

900 

1.99 

972 

2.35 

1111 

3.11 

2200 

3930 

.302 

657 

1.14 

740 

1.40 

817 

1.70 

892 

2.03 

966 

2.40 

1103 

3.17 

2300 

4110 

.330 

660 

1.22 

737 

1.47 

814 

1.77 

886 

2.10 

960 

2.46 

1089 

3.23 

2400 

4290 

.360 

663 

1.30 

737 

1.53 

812 

1.84 

880 

2.17 

949 

2.52 

1083 

3.31 

2500 

4470 

.390 

666 

1.40 

737 

1.63 

809 

1.91 

877 

2.23 

946 

2.60 

1074 

3.38 

2600 

4640 

.422 

672 

1.48 

740 

1.72 

806 

2.00 

874 

2.32 

940 

2.67 

1069 

3.46 

2800 

5000 

.489 

686 

1.70 

746 

1.95 

809 

2.22 

869 

2.50 

934 

2.86 

1057 

3.63 

3000 

5360 

.560 

703 

1.96 

757 

2.19 

814 

2.46 

874 

2.74 

932 

3.06 

1052 

3.84 

3200 

5720 

.638 

717 

2.24 

772 

2.49 

823 

2.75 

877 

3.04 

934 

3.36 

1043 

4.08 

3400 

6070 

.721 

740 

2.59 

789 

2.81 

840 

3.08 

886 

3.36 

937 

3.66 

1040 

4.36 

3600 

6430 

.810 

757 

2.97 

809 

3.19 

854 

3.44 

900 

3.75 

949 

4.03 

1046 

4.73 

3800 

6790 

.900 

872 

3.86 

914 

4.14 

957 

4.46 

1052 

5.12 

4000 

7140 

1.000 

932 

4.61 

972 

4.90 

1057 

5.59 

APPENDIX 


315 


TABLE  XVI. — No.  4  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"S.P. 

K"  S.  P. 

X-S.P. 

H"  S.  P. 

K!1  S.  P. 

w  s.  P. 

a 
A 

ft 

w 

a 

ft 

w 

a 

S 

a 

it 

a 

ft 

a 

ft 

w 

1000 

2330 

.063 

290 

.17 

363 

.26 

1100 

2570 

.076 

288 

.19 

358 

.28 

1200 

2800 

.090 

290 

.21 

358 

.30 

418 

.41 

1300 

3030 

.106 

295 

.24 

353 

.33 

413 

.44 

468 

.56 

1400 

3270 

.122 

300 

.28 

355 

.36 

410 

.47 

463 

.59 

515 

.74 

1500 

3500 

.141 

308 

.32 

358 

.40 

408 

.50 

460 

.62 

510 

.77 

558 

.92 

1600 

3730 

.160 

315 

.37 

360 

.45 

410 

.55 

458 

.66 

505 

.80 

550 

.96 

1700 

3970 

.180 

323 

.42 

368 

.50 

413 

.60 

455 

.71 

503 

.85 

545 

1.00 

1800 

4220 

.202 

333 

.49 

375 

.56 

415 

.66 

458 

.77 

500 

.90 

543 

1.05 

1900 

4430 

.225 

343 

.55 

383 

.63 

420 

.73 

460 

.84 

500 

.96 

540 

1.11 

2000 

4670 

.250 

353 

.62 

390 

.71 

428 

.81 

463 

.92 

500 

1.04 

540 

1.17 

2100 

4900 

.275 

363 

.70 

398 

.80 

435 

.89 

468 

1.00 

503 

1.12 

540 

1.26 

2200 

5130 

.302 

373 

.78 

408 

.88 

443 

.98 

475 

1.08 

508 

1.21 

543 

1.35 

2300 

5370 

.330 

385 

.87 

418  .98 

450  1.08 

483 

1.19 

513 

1.31 

545 

1  .  44 

2400 

5600 

.360 

395 

.97 

428 

1.09 

458 

1.19 

488 

1.30 

518 

1.42 

550 

1.55 

2500 

5830 

.390 

408 

1.07 

438 

1.19 

468 

1.32 

495 

1.41 

525 

1.53 

555 

1.67 

2600 

6070 

.422 

420 

1.19 

448 

1.32 

475 

1.43 

505 

1.56 

533 

1.67 

560 

1.81 

2800 

6530 

.489 

443 

1.44 

468 

1.58 

495 

1.71 

520 

1.84 

548 

1.95 

575 

2.08 

3000 

7000 

.560 

468 

1.76 

493 

1.86 

515 

2.03 

540 

2.16 

565 

2.29 

585 

2.42 

3200 

7460 

.638 

538 

2.37 

560 

2.53 

585 

2.67 

608 

2.82 

3400 

7930 

.721 

605 

3.11 

625 

3.27 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air. 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

1K"S.P. 

1H"S.  P. 

WS.P. 

2"  S.  P. 

2H"S.P. 

a 
o. 
« 

ft 

B 

a 
ft 

« 

ft 

w 

a 

ft 
« 

ft 

w 

a 

ft 
« 

ft 

w 

a 
d 
rt 

ft 

K 

a 
P. 
« 

ft 

1300 

3030 

.106 

615 

1.03 

1400 

3270 

.122 

608 

1.06 

690 

1.41 

770 

1.78 

1500 

3500 

.141 

600 

1.09 

685 

1.44 

763 

1.84 

833 

2.23 

1600 

3730 

.160 

595 

1.13 

678 

1.50 

755 

1.89 

825 

2.29 

893 

2.72 

1700 

3970 

.180 

588 

1.17 

670 

1.53 

748 

1.94 

815 

2.34 

883 

2.80 

1008 

3.78 

1800 

4220 

.202 

583 

1.22 

663 

1.58 

738 

1.94 

808 

2.40 

875 

2.87 

998 

3.84 

1900 

4430 

.225 

580 

1.27 

658 

1.63 

733 

2.03 

800 

2.47 

868 

2.93 

988 

3.91 

2000 

4670 

.250 

578 

1.33 

655 

1.70 

728 

2.08 

793 

2.53 

858 

2.99 

978 

3.99 

2100 

4900 

.275 

578 

1.40 

650 

1.76 

720 

2.16 

7882.59 

850 

3.07 

973 

4.07 

2200 
2300 

5130 
5370 

.302 
.330 

575 

578 

1.49 
1.59 

648 
645 

1.83 
1.92 

7152.23 
7132.31 

7802.66 
7752.74 

845 
840 

3.14 
3.22 

965 
953 

4.15 
4.23 

2400 

5600 

.360 

580 

1.70 

645 

2.00 

710 

2.40 

770 

2.83 

830 

3.30 

948 

4.32 

2500 

5830 

.390 

583 

1.83 

645 

2.13 

708 

2.50 

768 

2.91 

828 

3.39 

940 

4.42 

2600 

6070 

.422 

588 

1.94 

6482.24 

7052.61 

76513.03 

823 

3.49 

935 

4.51 

2800 

6530 

.489 

600 

2.23 

653 

2.55 

708 

2.90 

760 

3.27 

818 

3.73 

925 

4.74 

3000 

7000 

.560 

615 

2.56 

663 

2.87 

713 

3.22 

765 

3.59 

815 

4.00 

920 

5.01 

3200 

7460 

.638 

628 

2.93 

675 

3.25 

7203.59 

768 

3.97 

818 

4.39 

913 

5.33 

3400 

7930 

.721 

648 

3.38 

690 

3.67 

735 

4.02 

775 

4.39 

820 

4.79 

910 

5.70 

3600 

8400 

.810 

663 

3.87 

708 

4.16 

748 

4.50 

788 

4.90 

830 

5.27 

915 

6.18 

3800 

8860 

.900 

7635.04 

8005.41 

838 

5.83 

920 

6.69 

4000 

9330 

1.000 

815 

6.02 

850 

6.40 

925 

7.30 

316 


HEATING  AND  VENTILATION 


TABLE  XVII. — No.  4^  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES 
AND  STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
mm. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

«"S.P. 

«"S.P. 

W  s.  P. 

H"  S.  P. 

H"  S.  P. 

K"  s.  P. 

a 

a 
« 

ft 

M 

ft 
ffi 

£ 

ft 
tf 

ft 

a 
| 

& 

a 

S 

a 
W 

a 
d 
tf 

ft 

w 

1000 

2950 

.063 

258 

.21 

322 

.33 

1100 

3250 

.076 

256 

.23 

318 

.35 

1200 

3540 

.090 

258 

.27 

318 

.38 

371 

.52 

1300 

3840 

.106 

262 

.30 

313 

.41 

367 

.55 

416 

0.71 

1400 

4130 

.122 

267 

.35 

316 

.46 

365 

.59 

411 

0.75 

458 

0.93 

1500 

4430 

.141 

273 

.40 

318 

.51 

362 

.63 

409 

0.79 

453 

0.97 

496 

1.17 

1600 

4720 

.160 

280 

.46 

320 

.57 

365 

.69 

407 

0.84 

449 

.02 

489 

1.21 

1700 

5020 

.180 

287 

.53 

327 

.64 

367 

.76 

4050.90 

447 

.07 

485 

1.27 

1800 

5310 

.202 

296 

.61 

333 

.71 

369 

.84 

407|0.97 

445 

.14 

482 

1.33 

1900 

5610 

.225 

305 

.69 

340 

.80 

373 

.92 

409 

1.06 

445 

.22 

480 

1.40 

2000 

5900 

.250 

313 

.79 

347 

.89 

380 

1.02 

411  1.16 

445 

.31 

480 

1.48 

2100 

6200 

.275 

322 

.88 

353 

1.01 

387 

1.13 

416 

1.26 

447 

.42 

480 

1.59 

2200 

6500 

.302 

331 

.98 

362 

1.12 

393 

1.24 

422 

1.37 

451 

.53 

482 

1.71 

2300 

6790 

.330 

342 

1.10 

371 

1.24 

400 

1.37 

429  1.50 

456 

.65 

485 

1.82 

2400 

7090 

.360 

351 

1.23 

380 

1.38 

407 

1.51 

433 

1.64 

460 

.80 

489 

1.96 

2500 

7380 

.390 

362 

1.35 

389 

1.50 

416 

1.67 

440 

1.79 

467 

1.94 

493 

2.11 

2600 

7680 

.422 

373 

1.51 

398 

1.67 

422 

1.81 

449'  1.97 

473 

2.11 

498 

2.29 

2800 

8270 

.489 

393 

1.82 

416 

2.00 

440 

2.17 

462 

2.33 

487 

2.47 

511 

2.63 

3000 

8860 

.560 

416 

2.23 

438 

2.35 

458 

2.57 

480 

2.73 

502 

2.90 

520 

3.06 

3200 

9450 

.638 

478 

3.00 

498  3.20 

520 

3.38 

540 

3.57 

3400 

10040 

.721 

538 

3.93 

556 

4.13 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

1>£"S.P. 

1H"  S.  P. 

\W  S.  P. 

2"  S.  P. 

2>$"S.P. 

a 
a 

H 

ft 

W 

a 
a 
P£ 

S 

a 

a 
tf 

a 
W 

a 

a 
tf 

a 

a 

a 
M 

a 
W 

a 

a 
H 

a 
W 

1300 

3840 

.106 

547 

1.30 

1400 

4130 

.122 

540 

1.34 

613 

1.79 

685 

2.25 

1500 

4430 

.141 

533 

1.38 

609 

1.82 

678 

2.33 

740 

2.82 

1600 

4720 

.160 

529 

1.43 

602 

1.89 

671 

2.39 

733 

2.90 

793 

3.44 

1700 

5020 

.180 

522 

1.48 

596 

1.93 

665 

2.45 

725 

2.96 

785 

3.54 

896 

4.78 

1800 

5310 

.202 

518 

1.54 

589 

2.00 

656 

2.51 

718 

3.04 

778 

3.63 

887 

4.86 

1900 

5610 

.225 

516 

1.60 

585 

2.07 

651 

2.57 

711 

3.12 

771 

3.71 

878 

4.94 

2000 

5900 

.250 

513 

1.69 

582 

2.15 

647 

2.63 

704 

3.20 

762 

3.79 

869 

5.04 

2100 

6200 

.275 

513 

1.78 

578 

2.23 

640 

2.74 

700 

3.28 

756 

3.89 

865 

5.14 

2200 

6500 

.302 

511 

1.89 

576 

2.31 

636 

2.82 

696 

3.36 

751 

3.97 

858 

5.25 

2300 

6790 

.330 

513 

2.01 

573  2.43 

633 

2.92 

68913.46 

747 

4.07 

847 

5.35 

2400 

7090 

.360 

5143 

2.15 

573 

2.53 

631 

3.04 

685 

3.59 

738 

4.17 

842 

5.47 

2500 

7380 

.390 

518 

2.31 

573 

2.69 

629 

3.16 

682 

3.69 

736 

4.29 

836 

5.59 

2600 

7680 

.422 

522 

2.45 

576 

2.84 

627 

3.30 

680 

3.83 

731 

4.42 

831 

5.71 

2800 

8270 

.489 

533 

2.82 

580 

3.22 

629 

3.67 

676 

4.13 

727 

4.72 

822 

5.99 

3000 

8860 

.560 

547 

3.24 

589 

3.63 

633 

4.07 

680 

4.54 

725 

5.06 

818 

6.34 

3200 

9450 

.638 

558 

3.71 

600 

4.11 

640 

4.54 

682 

5.02 

727 

5.55 

811 

6.74 

3400 

10040 

.721 

576 

4.27 

613 

4.64 

653 

5.08 

689 

5.55 

729 

6.06 

809 

7.21 

3600 

10630 

.810 

589 

4.90 

629 

5.27 

665 

5.69 

700 

6.20 

738 

6.66 

813 

7.82 

3800 

11220 

.900 

678 

6.38 

711 

6.85 

745 

7.37 

818 

8.46 

4000 

11810 

1.000 

725 

7.61 

756 

8.10 

822 

9.23 

APPENDIX 


317 


TABLE   XVIII. — No.   5   NIAGARA  CONOIDAL  FAN    (TYPE  N)  CAPACITIES 
AND  STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"  s.  P. 

K"  s.  P. 

W  S.  P. 

H"  S.  P. 

W  S.  P. 

H"S.P. 

a 
a 
« 

ft 

w 

a 

a 
M 

ft 

X 

a 
A 
« 

ft 

w 

a 
P. 
« 

ft 

W 

a 
d 
d 

ft 

W 

a 
p. 
f4 

S 

1000 

3640 

.063 

232 

.26 

290 

.41 

1100 

4010 

.076 

230 

.29 

286 

.44 

1200 

4370 

.090 

232 

.33 

286 

.47 

334 

.65 

1300 

4740 

.106 

236 

.38 

282 

.51 

330 

.68 

374 

.88 

1400 

5100 

.122 

240 

.43 

284 

.56 

328 

.73 

370 

.92 

412 

1.15 

1500 

5470 

.141 

246 

.50 

286 

.63 

326 

.78 

368 

.98 

408 

1.20 

446 

1.44 

1600 

5830 

.160 

252 

.57 

288 

.70 

328 

.86 

366 

1.04 

404 

1.26 

440 

1.49 

1700 

6190 

.180 

258 

.66 

294 

.79 

330 

.94 

364 

1.11 

402 

1.33 

436 

1.57 

1800 

6560 

.202 

266 

.76 

300 

.88 

332 

1.03 

366 

1.20 

400 

1.40 

434 

1.64 

1900 

6930 

.225 

274 

.86 

306 

.99 

336 

1.14 

368 

1.31 

400 

1.50 

432 

1.73 

2000 

7290 

.250 

282 

.97 

312 

1.11 

342 

1.26 

370 

1.43 

400 

1.62 

432 

1.83 

2100 

7660 

.275 

2901.09 

318 

1.24 

348 

1.39 

374 

1.56 

402 

1.75 

432 

1.96 

2200 

8010 

.302 

298 

1.21 

326 

1.38 

354 

1.53 

380 

1.69 

406 

1.89 

434 

2.11 

2300 

8380 

.330 

308 

1.36 

334 

1.55 

360 

1.69 

386 

1.85 

410 

2.04 

436 

2.25 

2400 

8750 

.360 

316 

1.51 

342 

1.70 

366 

1.86 

390 

2.03 

414 

2.22 

440 

2.41 

2500 

9100 

.390 

326 

1.67 

350 

1.86 

374 

2.06 

396 

2.21 

420 

2.40 

444 

2.60 

2600 

9480 

.422 

336 

1.86 

3582.06 

380 

2.24 

404 

2.43 

426 

2.60 

448 

2.83 

2800 

10200 

.489 

354 

2.25 

374 

2.46 

396 

2.68 

416 

2.88 

438 

3.05 

460 

3.25 

3000 

10940 

.560 

374 

2.75 

394 

2.90 

412 

3.18 

432 

3.38 

452 

3.58 

468 

3.78 

3200 

11660 

.638 

430 

3.70 

448 

3.95 

468 

4.18 

486 

4.40 

3400 

12390 

.721 

484 

4.85 

500 

5.10 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

IK"  S.  P. 

WS.  P. 

W  8.  P. 

2"  S.  P. 

2^"  S.  P. 

a 

ft 
« 

ft 

W 

a 
A 

rt 

ft 
W 

a 
p. 
« 

ft 

a 
o, 
ri 

ft 

W 

a 
Q. 
« 

ft 
W 

a 

o. 

PS 

ft 

W 

1300 

4740 

.106 

492 

1.60 

1400 

5100 

.122 

486 

1.65 

552 

2.21 

616 

2.78 

1500 

5470 

.141 

480 

1.71 

548 

2.25 

610 

2.88 

666 

3.48 

1600 

5830 

.160 

476 

1.76 

542 

2.34 

604 

2.95 

660 

3.58 

714 

4.25 

1700 

6190 

.180 

470 

1.82 

536 

2.39 

5983.03 

652 

3.65 

706 

4.38 

806 

5.90 

1800 

6560 

.202 

466 

1.90 

530 

2.47 

590 

3.10 

646 

3.75 

700 

4.48 

798 

6.00 

1900 

6930 

.225 

464 

1.98 

526 

2.55 

586 

3.18 

640 

3.85 

694 

4.58 

790 

6.10 

2000 

7290 

.250 

462 

2.08 

524  2  .  65 

582  3.25 

634 

3.95 

686 

4.68 

782 

6.23 

2100 

7660 

.275 

462 

2.19 

520 

2.75 

576 

3.38 

630 

4.05 

680 

4.80 

778 

6.35 

2200 

8010 

.302 

460 

2.33 

518 

2.85 

572 

3.48 

624 

4.15 

676 

4.90 

772 

6.48 

2300 

8380 

.330 

4622.48 

516  3.00 

5703.60 

620 

4.28 

672 

5.03 

762 

6.60 

2400 

8750 

.360 

464 

2.65 

516 

3.13 

5683.75 

616 

4.44 

664 

5.15 

758 

6.75 

2500 

9100 

.390 

466 

2.85 

516 

3.33 

56613.90 

614 

4.55 

662 

5.30 

752 

6.90 

2600 

9480 

.422 

470 

3.03 

518 

3.50 

564 

4.08 

612 

4.73 

658 

5.45 

748 

7.05 

2800 

10200 

.489 

480 

3.48 

522 

3.98 

566 

4.53 

608 

5.10 

654 

5.83 

740 

7.40 

3000 

10940 

.560 

492 

4.00 

530 

4.48 

570 

5.03 

612 

5.60 

652 

6.25 

736 

7.83 

3200 

11660 

.638 

502 

4.57 

540 

5.08 

576 

5.60 

614 

6.20 

654 

6.85 

730 

8.32 

3400 

12390 

.721 

518 

5.27 

552 

5.73 

588 

6.28 

620 

6.85 

656 

7.48 

728 

8.90 

3600 

13120 

.810 

530 

6.05 

566 

6.50 

598 

7.03 

630 

7.65 

664 

8.22 

732 

9.65 

3800 

13850 

.900 

610 

7.88 

640 

8.46 

670 

9.10 

736 

10.5 

4000 

14580 

1.000 

652 

9.40 

680 

10.0 

740 

11.4 

318 


HEATING  AND  VENTILATION 


TABLE  XIX. — No.  5H  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES 
AND  STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"  s.  P. 

K"S.P. 

K"  s.  P. 

K"S.P. 

K"  S.  P. 

%"S.P. 

a 
& 
PJ 

d 

a 

fk 

0j 

d 
W 

a 

d 
M 

d 

W 

a 

d 
rf 

d 
W 

a 

d 
tf 

d 
W 

a 

d 

ri 

d 

B 

1000 

4410 

.063 

211 

.32 

264 

.49 

1100 

4850 

.076 

209 

.35 

260 

.53 

1200 

5290 

.090 

211 

.40 

260 

.57 

304 

.78 

1300 

5730 

.106 

215 

.45 

257 

.62 

300 

.83 

340 

1.06 

1400 

6170 

.122 

218 

.52 

258 

.68 

298 

.88 

336 

1.12 

375 

1.40 

1500 

6620 

.141 

224 

.60 

260 

.76 

296 

.95 

335 

1.18 

371 

1.45 

406 

1.75 

1600 

7060 

.160 

229 

.69 

262 

.85 

298 

1.04 

333 

1.26 

367 

.52 

400 

1.81 

1700 

7500 

.180 

235 

.80 

267 

.95 

300 

1.13 

331 

.35 

366 

.60 

397 

1.89 

1800 

7940 

.202 

242 

.92 

273 

1.06 

302 

1.25 

333 

.46 

364 

.70 

395 

1.98 

1900 

8380 

.225 

249 

1.04 

278 

1.19 

306 

1.38 

335 

.59 

364 

.82 

393 

2.09 

2000 

8820 

.250 

256 

1.17 

284 

1.34 

311 

1.53 

336 

.73 

364 

.96 

393 

2.21 

2100 

9260 

.275 

264 

1.32 

289 

1.50 

316 

1.68 

340 

.88 

366 

2.12 

393 

2.37 

2200 

9700 

.302 

271 

1.47 

296 

1.67 

322 

1.85 

346 

2.05 

369 

2.28 

395 

2.55 

2300 

10140 

.330 

280 

1.65 

304 

1.86 

327 

2.05 

351 

2.24 

373 

2.47 

397 

2.72 

2400 

10590 

.360 

287 

1.83 

311 

2.05 

333 

2.25 

355 

2.45 

377 

2.68 

400 

2.92 

2500 

11030 

.390 

297 

2.02 

318 

2.25 

340 

2.49 

360 

2.67 

382 

2.90 

404 

3.15 

2600 

11470 

.422 

306 

2.25 

326 

2.49 

346 

2.71 

367 

2.94 

387 

3.15 

407 

3.42 

2800 

12350 

.489 

322 

2.72 

340 

2.98 

360 

3.24 

378 

3.48 

398 

3.69 

418 

3.93 

3000 

13230 

.560 

340 

3.33 

358 

3.51 

375 

3.84 

393 

4.08 

411 

4.33 

426 

4.57 

3200 

14110 

.638 

391 

4.48 

407 

4.78 

426 

5.05 

442 

5.33 

3400 

15000 

.721 

440 

5.87 

455 

6.17 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

I",  S.  P. 

IK"  S.  P. 

1M"S.P. 

IK"  S.  P. 

2"  S.  P  . 

M2"  S.  P. 

i 

M 

d 

B 

a 

d 
H 

d 
B 

a 

d 
M 

d 
B 

a 

d 
tf 

d 

B 

a 

d 

ti 

d 

B 

i 

d 

d 

d 
B 

1 

1300 

5730 

.106 

44711.94 

1400 

6170 

.122 

442  1.99 

502 

2.67 

560 

3.36 

1500 

6620 

.141 

437 

2.07 

498 

2.72 

555 

3.48 

606 

4.21 

1600 

7060 

.160 

433 

2.13 

493 

2.83 

549 

3.57 

600 

4.33 

649 

5.14 

1700 

7500 

.180 

4272.20 

4872.89 

544 

3.66 

59314.42 

642 

5.29 

733 

7.14 

1800 

7940 

.202 

424 

2.30 

482 

2.99 

537 

3.75 

587 

4.54 

636 

5.42 

726 

7.26 

1900 

8380 

.225 

422 

2.39 

478 

3.09 

533 

3.84 

582 

4.66 

631 

5.54 

718 

7.38 

2000 

8820 

.230 

420 

2.52 

476 

3.21 

529 

3.93 

576 

4.78 

624 

5.66 

711 

7.53 

2100 

9260 

.275 

420 

2.65 

473 

3.33 

524 

4.08 

573 

4.90 

618 

5.81 

707 

7.68 

2200 

9700 

.302 

418 

2.82 

471 

3.45 

520 

4.21 

567 

5.02 

615 

5.93 

702 

7.84 

2300 

10140 

.330 

4203.00 

469 

3.63 

518 

4.36 

564 

5.17 

611 

6.08 

693 

7.99 

2400 

10590 

.360 

422 

3.21 

469 

3.78 

517 

4.54 

560 

5.35 

604 

6.23 

689 

8.17 

2500 

11030 

.390 

424 

3.45 

469 

4.02 

515 

4.72 

558 

5.51 

602 

6.41 

684 

8.35 

2600 

11470 

.422 

427 

3.66 

471 

4.24 

513 

4.93 

557 

5.72 

598 

6.59 

6808.53 

2800 

12350 

.489 

437 

4.21 

475 

4.81 

515 

5.48 

553 

6.17 

595 

7.05 

673 

8.95 

3000 

13230 

.560 

447 

4.84 

482 

5.42 

518 

6.08 

557 

6.78 

593 

7.56 

669 

9.47 

3200 

14110 

.638 

456 

5.54 

491  6.14 

524 

6.78 

558 

7.50 

595 

8.29 

664 

10.1 

3400 

15000 

.721 

471 

6.38 

502 

6.93 

535 

7.59 

564 

8.29 

596 

9.04 

662 

10.8 

3600 

15880 

.810 

482 

7.32 

515 

7.87 

544 

8.50 

573 

9.26 

604 

9.95 

666 

11.7 

3800 

16760 

.900 

555 

9.53 

582 

10.2 

609 

11.0 

669 

12.7 

4000 

17640 

1.000 

593 

11.4 

618 

12.1 

673 

13.8 

APPENDIX 


319 


TABLE  XX. — No.  6  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

X"  S.  P. 

H"  S.  P. 

K"  s.  P. 

W 

a 

d 
pi 

S.  P. 

H"  S.  P. 

H"  s.  P. 

a 
P. 
« 

d 
H 

6 

i4 

PJ 

S 

B 

0, 

rt 

S 

d 

a 

d 
« 

d 
W 

a  1 

4  1  d 

tf  1  W 

1000 

5250 

.063 

193 

.37 

242 

.59 

1100 

5770 

.076 

192 

.42 

238 

.63 

1200 

6300 

.090 

193 

.48 

238 

.67 

278 

.93 

1300 

6820 

.106 

197 

.54 

235 

.73 

275 

.98 

312 

1.27 

1400 

7350 

.122 

200 

.62 

237 

.81 

274 

1.05 

308 

1.33 

344 

1.66 

1500 

7870 

.141 

205 

.72 

238 

.91 

272 

1.13 

307 

1.41 

340 

1.72 

372 

2.08 

1600 

8400 

.160 

210 

.82 

240 

1.01 

274 

1.23 

305 

1.49 

337 

1.81 

367 

2.15 

1700 

8920 

.180 

215 

.95 

245 

.13 

275 

1.35 

304 

1.60 

335 

1.91 

363 

2.25 

1800 

9450 

.202 

222 

1.09 

250 

.26 

277 

1.49 

305 

1.73 

334 

2.02 

362 

2.36 

1900 

9970 

.225 

228 

.24 

255 

.42 

280 

1.64 

307 

1.88 

334 

2.16 

360 

2.49 

2000 

10500 

.250 

235 

.40 

260 

.59 

285 

1.82 

309 

2.06 

334 

2.33 

3602.63 

2100 

11030 

.275 

242 

.57 

265 

.79 

290 

2.00 

312 

2.24 

335 

2.52 

360 

2.82 

2200 

11550 

.302 

248 

.75 

272 

1.98 

295 

2.20 

317 

2.43 

339 

2.72 

362 

3.04 

2300 

12070 

.330 

257 

.96 

279 

2.21 

300 

2.43 

322 

2.66 

342 

2.94 

363 

3.23 

2400 

12600 

.360 

263 

2.18 

285 

2.45 

305 

2.68 

325 

2.92 

345 

3.19 

367 

3.48 

2500 

13120 

.390 

272 

2.41 

291 

2.67 

312 

2.96 

330 

3.18 

350 

3.45 

370 

3.74 

2600 

13650 

.422 

280 

2.68 

299 

2.96 

317 

3.22 

337 

3.50 

355 

3.74 

374 

4.07 

2800 

14700 

.489 

295 

3.24 

312 

3.55 

330 

3.85 

347 

4.14 

365 

4.39 

384 

4.68 

3000 

15750 

.560 

312 

3.96 

329 

4.18 

344 

4.57 

360 

4.86 

377 

5.15 

390 

5.44 

3200 

16790 

.638 

359 

5.33 

373 

5.69 

390 

6.01 

405 

6.34 

3400 

17850 

.721 

403 

6.98 

417 

7.35 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"S.  P. 

1K"S.P. 

1K"S.P. 

1H"  S.  P. 

2"  S.P. 

2W  S.  P. 

a 

d 
tf 

d 
W 

a 

d 
tf 

d 
W 

a 

d 
tf 

d 

W 

a 

d 
tf 

d 
W 

a 

d 
« 

d 
W 

B 

d 

ri 

d 
a 

1300 

6820 

.106 

410 

2.31 

1400 

7350 

.122 

405.2.37 

460 

3.18 

513 

4.00 

1500 

7870 

.141 

400 

2.46 

457 

3.24 

509 

4.14 

555 

5.00 

1600 

8400 

.160 

397 

2.54 

452 

3.36 

504 

4.25 

550 

5.15 

595 

6.12 

1700 

8920 

.180 

3922.62 

447 

3.44 

499 

4.36 

544 

5.26 

589 

6.30 

6728.50 

1800 

9450 

.202 

389 

2.73 

442 

3.56 

492 

4.47 

539 

5.40 

584 

6.45 

6658.64 

1900 

9970 

.225 

387 

2.85 

439 

3.67 

489 

4.57 

534 

5.55 

579 

6.59 

659 

8.78 

2000 

10500 

.250 

3853.00 

437 

3.82 

485 

4.68 

529 

5.69 

572  6.73 

652 

8.96 

2100 

11030 

.275 

385 

3.16 

434 

3.96 

480 

4.86 

525 

5.83 

567 

6.91 

649 

9.14 

2200 

11550 

.302 

384 

3.35 

432 

4.11 

477 

5.00 

520 

5.98 

564 

7.06 

644 

9.32 

2300 

12070 

.330 

3853.57 

430 

4.32 

475 

5.18 

517 

6.16 

5607.24 

63519.50 

2400 

12600 

.360 

387 

3.82 

430 

4.50 

474 

5.40 

514 

6.37 

554 

7.42 

632 

9.72 

2500 

13120 

.390 

389 

4.10 

430 

4.79 

472 

5.62 

512 

6.55 

552 

7.63 

627 

9.94 

2600 

13650 

.422 

392 

4.36 

432 

5.04 

470 

5.87 

510 

6.81 

549  7.85 

624|10.2 

2800 

14700 

.489 

400  5.00 

435 

5.73 

.472 

6.52 

507 

7.34 

545 

8.39 

617  10.7 

3000 

15750 

.560 

410 

5.76 

442 

6.45 

475 

7.24 

510 

8.06 

544 

9.00 

614 

11.3 

3200 

16790 

.638 

419  6.59 

450 

7.31 

480 

8.06 

5128.93 

5459.86 

609  12.0 

3400 

17850 

.721 

432 

7.60 

460 

8.24 

490 

9.04 

517 

9.86 

547 

10.8 

607 

12.8 

3600 

18900 

.810 

442 

8.71 

472 

9.36 

499 

10.1 

525 

11.0 

554 

11.9 

610 

13.9 

3800 

19950 

.900 

509 

11.3 

534 

12.2 

559 

13.1 

614'15.1 

4000 

21000 

1.000 

544 

13.5 

567 

14.4 

617 

16.4 

320 


HEATING  AND  VENTILATION 


TABLE  XXI. — No.  7  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft. 
per  min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 

for 
total 
press. 

K"  s.  P. 

H"  S.  P. 

H"  S.  P. 

H"  S.  P. 

H"  S.  P. 

K"  S.  P. 

a 
a 
« 

ft 

w 

a 
a 
» 

ft 
W 

a 

s 

ft 

W 

d 
« 

S 

a 
o. 

P4 

S 

a 
ci 
« 

ft 

W 

1000 

7140 

.063 

166 

.51 

207 

.80 

1100 

7860 

.076 

164 

.57 

204 

.85 

1200 

8570 

.090 

166 

.65 

204 

.92 

239 

1.26 

1300 

9290 

.106 

169 

.74 

202 

1.00 

236 

1.34 

267 

1.73 

1400 

10000 

.122 

172 

.35 

203 

1.10 

234 

1.43 

264 

1.81 

294 

2.26 

1500 

10720 

.141 

176 

.98 

204 

1.24 

233 

1.53 

263 

1.91 

292 

2.34 

319 

2.83 

1600 

11430 

.160 

180 

1.12 

206 

1.37 

234 

1.68 

262 

2.03 

289 

2.46 

314 

2.93 

1700 

12150 

.180 

184 

1.29 

210  1.54 

236 

1.83 

260 

2.18 

287 

2.60 

312 

3.07 

1800 

12860 

.202 

190 

1.49 

214 

1.72 

237 

2.02 

262 

2.36 

286 

2.75 

310 

3.21 

1900 

13570 

.225 

196 

1.68 

219 

1.93 

240 

2.23 

263 

2.56 

286 

2.95 

309 

3.39 

2000 

14290 

.250 

202 

1.90 

223  2.17 

244 

2.47 

264 

2.80 

286 

3.18 

309 

3.58 

2100 

15000 

.275 

207 

2.13 

227 

2.44 

249 

2.73 

267 

3.05 

287 

3.43 

309 

3.84 

2200 

15720 

.302 

213 

2.38 

233 

2.70 

253 

3.00 

272 

3.31 

290 

3.70 

310 

4.13 

2300 

16430 

.330 

220 

2.67 

239  3.01 

257 

3.31 

276 

3.63 

293 

4.00 

312 

4.40 

2400 

17150 

.360 

226 

2.97 

244j3.33 

262 

3.64 

279 

3.97 

296 

4.34 

314 

4.73 

2500 

17860 

.390 

233 

3.27 

250 

3.64 

267 

4.03 

283 

4.33 

300 

4.70 

317 

5.10 

2600 

18580 

.422 

240 

3.64 

256 

4.03 

272 

4.39 

289 

4.77 

304 

5.10 

320 

5.54 

2800 

20000 

.489 

253 

4.41 

267 

4.83 

283 

5.24 

297 

5.64 

313 

5.98 

329 

6.37 

3000 

21430 

.560 

267 

5.39 

282 

5.68 

294 

6.22 

309 

6.62 

323 

7.01 

334 

7.40 

3200 

22860 

.638 

307 

7.25 

320 

7.74 

334 

8.18 

347 

8.62 

3400 

24290 

.721 

346 

9.51 

357 

10.0 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

WS.P. 

IK"  S.  P. 

l?i"  S.  P. 

2"  S.  P. 

2K"S.P. 

a 
d, 
« 

ft 

W 

a 
o< 
* 

ft 

W 

a 
p< 

P4 

ft 

W 

a 

d 
ti 

ft 
W 

a 
d 
» 

ft 

W 

a 
P. 
« 

S 

1300 

9290 

.106 

352 

3.14 

1400 

10000 

.122 

347 

3.23 

394 

4.33 

440 

5.44 

1500 

10720 

.141 

343 

3.35 

392 

4.41 

436 

5.64 

476 

6.81 

1600 

11430 

.160 

340 

3.46 

387 

4.58 

432 

5.78 

472 

7.01 

510 

8.33 

1700 

12150 

.180 

336 

3.57 

383 

4.68 

427 

5.93 

466 

7.15 

504 

8.58 

576 

11.6 

1800 

12860 

.202 

333 

3.72 

379 

4.85 

422 

6.08 

462 

7.35 

500 

8.77 

570 

11.8 

1900 

13570 

.225 

332 

3.88 

376 

5.00 

419 

6.22 

457 

7.55 

496 

8.97 

564 

12.0 

2000 

14290 

.250 

330 

4.08 

374 

5.19 

416 

6.37 

453 

7.74 

490 

9.16 

559 

12.2 

2100 

15000 

.275 

330 

4.30 

372 

5.39 

412 

6.62 

450 

7.94 

486 

9.41 

556 

12.5 

2200 

15720 

.302 

329 

4.56 

370 

5.59 

409 

6.81 

446 

8.13 

483 

9.60 

552 

12.7 

2300 

16430 

.330 

330 

4.86 

369 

5.88 

407 

7.06 

443 

8.38 

480 

9.85 

544 

12.9 

2400 

17150 

.360 

332 

5.19 

369 

6.13 

406 

7.35 

440 

8.67 

474 

10.1 

542 

13.2 

2500 

17860 

.390 

333 

5.59 

369 

6.52 

404 

7.64 

439 

8.92 

473 

10.4 

537 

13.5 

2600 

18580 

.422 

336 

5.93 

370 

6.86 

40317.99 

437 

9.26 

470 

10.7 

534 

13.8 

2800 

20000 

.489 

343 

6.81 

373 

7.79 

404 

8.87 

434 

10.0 

467 

11.4 

529 

14.5 

3000 

21430 

.560 

352 

7.84 

379 

8.77 

407 

9.85 

437 

11.0 

466 

12.3 

526 

15.3 

3200 

22860 

.638 

359 

8.97 

386 

9.95 

412 

11.0 

439 

12.2 

467 

13.4 

522 

16.3 

3400 

24290 

.721 

370 

10.3 

394 

11.2 

420 

12.3 

443 

13.4 

469 

14.7 

520 

17.4 

3600 

25720 

.810 

379 

11.9 

404 

12.7 

427 

13.8 

450 

15.0 

474 

16.1 

523 

18.9 

3800 

27150 

.900 

436 

15.4 

457 

16.6 

479 

17.8 

526 

20.5 

4000 

28580 

1.000 

466 

18.4 

486 

19.6 

529 

22.4 

APPENDIX 


321 


TABLE  XXII. — No.  8  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 

min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"  S.  P. 

H"  S.  P. 

M"  s.  P. 

X"  S.  P. 

W  S.  P. 

%"S.P. 

a 
a 
« 

ft 

w 

a 
P. 

«' 

a 

W 

a 
d 

e4 

S 

i 

« 

a 

w 

i 

« 

a 

w 

a 

a 
« 

a 
B 

1000 

9330 

.063 

145 

.67 

181 

1.04 

1100 

10270 

.076 

144 

.74 

179  1.11 

1200 

11200 

.090 

145 

.85 

179  1.20 

209 

1.65 

1300 

12130 

.106 

148 

.96 

176  1.31 

206 

1.75 

234 

2.25 

1400 

13060 

.122 

150 

1.11 

178  1.44 

205 

1.87 

231 

2.36 

258 

2.95 

1500 

14000 

.141 

154 

1.27 

179  1.61 

204 

2.00 

230 

2.50 

255 

3.06 

279 

3.69 

1600 

14930 

.160 

158 

1.47 

180  1.79 

205 

2.19 

229 

2.66 

253 

3.21 

275 

3.82 

1700 

15860 

.180 

161 

1.69 

184  2.01 

206 

2.39 

228 

2.85 

251 

3.39 

273 

4.01 

1800 

16800 

.202 

166 

1.94 

1882.25 

208 

2.64 

229 

3.08 

250 

3.59 

271 

4.19 

1900 

17730 

.225 

1712.20 

19l'2.52 

210 

2.91 

230 

3.34 

250 

3.85 

270 

4.42 

2000 

18660 

.250 

176  2.48 

1952.83 

214 

3.23 

231 

3.66 

250 

4.15 

270 

4.68 

2100 

19600 

.275 

181 

2.79 

199,3.18 

218 

3.56 

234 

3.98 

251 

4.48 

270 

5.02 

2200 

20530 

.302 

186 

3.11 

204 

3.53 

221 

3.92 

238 

4.33 

254 

4.83 

271 

5.40 

2300 

21460 

.330 

193 

3.48 

209  3.93 

225 

4.33 

241 

4.74 

256 

5.22 

273 

5.75 

2400 

22400 

.360 

198 

3.87 

214 

4.35 

229 

4.76 

244 

5.19 

259 

5.67 

275 

6.18 

2500 

23330 

.390 

204 

4.28 

219 

4.75 

234 

5.26 

248 

5.65 

263 

6.13 

278 

6.66 

2600 

24260 

.422 

210 

4.76 

224 

5.26 

238 

5.73 

253 

6.23 

266 

6.66 

280 

7.23 

2800 

26130 

.489 

221 

5.76 

234 

6.31 

248 

6.85 

260 

7.36 

274 

7.81 

288 

8.32 

3000 

28000 

.560 

234 

7.04 

246 

7.42 

258 

8.13 

270 

8.64 

283 

9.15 

293 

9.66 

3200 

29860 

.638 

269 

9.47 

280 

10.1 

293 

10.7 

304 

11.3 

3400 

31720 

.721 

303 

12.4 

313 

13.1 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

WS.P. 

1M"  S.P. 

IX"  S.  P. 

2"  S.  P. 

2M"S.P. 

a 

ft 
tf 

ft 

a 

a 
« 

£ 

a 
a 

P3 

ft 

B 

a 
d 

P3 

a 
B 

a 
4 

oj 

a 

B 

a 

a 
tf 

a 

B 

1300 

12130 

.106 

308 

4.10 

1400 

13060 

.122 

3044.22 

345 

5.65 

385  7.10 

1500 

14000 

.141 

300 

4.37 

343 

5.76 

381 

7.36 

416 

8.90 

1600 

14930 

.160 

298 

4.51 

339 

5.98 

378 

7.55 

413 

9.15 

446 

10.9 

1700 

15860 

.180 

294 

4.66 

335 

6.11 

374)7.74 

408  9  .  34 

441 

11.2 

504  15.1 

1800 

16800 

.202 

291 

4.86 

331 

6.33 

369 

7.94 

404 

9.60 

438 

11.5 

499 

15.4 

1900 

17730 

.225 

290 

5.06 

329 

6.53 

366 

8.13 

400 

9.86 

434 

11.7 

494 

15.6 

2000 

18660 

.250 

289!5.33 

328;  6.  78 

3648.32 

396  10.1 

429 

12.0 

489  15.9 

2100 

19600 

.275 

289 

5.61 

325 

7.04 

360 

8.64 

394 

10.4 

425 

12.3 

486 

16.3 

2200 

20530 

.302 

288 

5.96 

324 

7.30 

358 

8.90 

390 

10.6 

423 

12.6 

483 

16.6 

2300 

21460 

.330 

289'  6.  35 

323 

7.68 

356!  9.  22 

388  11.0 

420 

12.9 

476  16.9 

2400 

22400 

.360 

290 

6.78 

323 

8.00 

355 

9.60 

38511.3 

415 

13.2 

474 

17.3 

2500 

23330 

.390 

291 

7.30 

323 

8.51 

354 

9.98 

384 

11.7 

414 

13.6 

470 

17.7 

2600 

24260 

.422 

294 

7.74 

324 

8.96 

353 

10.4 

383 

12.1 

411 

14.0 

468 

18.1 

2800 

26130 

.489 

300 

8.90 

326 

10.2 

354 

11.6 

380 

13.1 

409 

14.9 

463 

19.0 

3000 

28000 

.560 

308 

10.2 

331 

11.5 

356 

12.9 

383 

14.3 

408 

16.0 

460 

20.0 

3200 

29860 

.638 

314 

11.7 

338 

13.0 

360 

14.3 

384 

15.9 

409 

17.5 

456 

21.3 

3400 

31720 

.721 

324 

13.5 

345 

14.7 

368 

16.1 

388 

17.5 

410 

19.1 

455 

22.8 

3600 

33590 

.810 

331 

15.5 

354 

16.6 

374 

18.0 

394 

19.6 

415 

21.1 

458 

24.7 

3800 

35460 

.900 

381 

20.2 

400 

21.6 

419 

23.3 

460 

26.8 

4000 

37330 

1.000 

408 

24.1 

425 

25.6 

463 

29.2 

322 


HEATING  AND  VENTILATION 


TABLE  XXIII. — No.  9  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 

min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

W  S.  P. 

H"  S.  P. 

Yz"  S.  P. 

W  S.  P. 

H"  S.  P. 

K"S.P. 

a 
a 

« 

ft 
W 

a 
d 
rt 

S 

a 

1 

ft 

w 

a 

& 
« 

ft 

K 

a 

ft 

PS 

W 

a 

d 

tf 

ft 

W 

1000 

11810 

.063 

129 

.84 

161 

1.32 

1100 

12990 

.076 

128 

.94 

159 

1.41 

1200 

14170 

.090 

129 

1.07 

159 

1.52 

186 

2.09 

1300 

15360 

.106 

131 

1.22 

157 

1.65 

183 

2.21 

208 

2.85 

1400 

16530 

.122 

133 

1.40 

158 

1.82 

182 

2.37 

206 

2.99 

229 

3.74 

1500 

17720 

.141 

137 

1.61 

159 

2.04 

181 

2.54 

205 

3.16 

227 

3.87 

248 

4.67 

1600 

18900 

.160 

140 

1.86 

160 

2.27 

182 

2.77 

203 

3.36 

225 

4.07 

244 

4.84 

1700 

20080 

.180 

143 

2.14 

163 

2.54 

183 

3.03 

202 

3.60 

223 

4.29 

242 

5.07 

1800 

21250 

.202 

148 

2.45 

167 

2.84 

185 

3.35 

203 

3.90 

222 

4.55 

241 

5.30 

1900 

22440 

.225 

152 

2.78 

170 

3.19 

187 

3.69 

205 

4.23 

222 

4.87 

240 

5.60 

2000 

23620 

.250 

1573.14 

173 

3.58 

190 

4.08 

206 

4.64 

222 

5.25 

240 

5.92 

2100 

24800 

.275 

161 

3.52 

177 

4.03 

193 

4.51 

208 

5.04 

223 

5.67 

240 

6.35 

2200 

25980 

.302 

166 

3.93 

181 

4.47 

197 

4.96 

211 

5.47 

226 

6.10 

241 

6.83 

2300 

27160 

.330 

171 

4.41 

186 

4.97 

200 

5.48 

215 

6.00 

228 

6.61 

242 

7.27 

2400 

28340 

.360 

176 

4.90 

190 

5.50 

203 

6.02 

217 

6.56 

230 

7.18 

244 

7.82 

2500 

29520 

.390 

181 

5.41 

195 

6.01 

208 

6.66 

220 

7.15 

233 

7.76 

247 

8.43 

2600 

30710 

.422 

187 

6.02 

199 

6.66 

211 

7.25 

224 

7.88 

237 

8.42 

249 

9.15 

2800 

33070 

.489 

197 

7.28 

208 

7.98 

220 

8.67 

231 

9.30 

243 

9.88 

256 

10.5 

3000 

35430 

.560 

208 

8.91 

219 

9.40 

229 

10.3 

240 

10.9 

251 

11.6 

260 

12.2 

3200 

37790 

.638 

239 

12.0 

249 

12.8 

260 

13.5 

270 

14.3 

3400 

40150 

.721 

269 

15.7 

278 

16.5 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

W  S.  P. 

1M"S.P. 

WS.P. 

2"  S.  P. 

2H"  S.  P. 

a 

a 
« 

ft 
W 

a 

P. 
« 

ft 
W 

a 
a 
ri 

ft 

W 

a 

a 
PS 

ft 

W 

a 
d 
PJ 

ft 

W 

a 
a 
« 

ft 

W 

1300 

15360 

.106 

273 

5.18 

1400 

16530 

.122 

270 

5.34 

307 

7.15 

342 

8.99 

1500 

17720 

.141 

267 

5.53 

304 

7.29 

339 

9.31 

370 

11.3 

1600 

18900 

.160 

264 

5.71 

301 

7.57 

336 

9.56 

367 

11.6 

397 

13.8 

1700 

20080 

.180 

261 

5.90 

298 

7.73 

332 

9.80 

362 

11.8 

392 

14.2 

448 

19.1 

1800 

21250 

.202 

259 

6.15 

294 

8.01 

328 

10.0 

359 

12.2 

389 

14.5 

443 

19.4 

1900 

22440 

.225 

258 

6.41 

292 

8.26 

326 

10.3 

356 

12.5 

386 

14.8 

439 

19.8 

2000 

23620 

.250 

257 

6.74 

291 

8.59 

323 

10.5 

352 

12.8 

381 

15.2 

435 

20.2 

2100 

24800 

.275 

257 

7.10 

289 

8.91. 

320 

10.9 

350 

13.1 

378 

15.6 

432 

20.6 

2200 

25980 

.302 

256 

7.54 

288 

9.23 

318 

11.3 

347 

13.4 

376 

15.9 

429 

21.0 

2300 

27160 

.330 

257 

8.04 

2879.72 

317S11.7 

344 

13.7 

373  16.3 

423 

21.4 

2400 

28340 

.360 

258 

8.59 

287 

10.1 

316 

12.2 

342 

14.3 

369 

16.7 

421 

21.9 

2500 

29520 

.390 

259 

9.23 

287 

10.8 

314 

12.6 

341 

14.8 

368 

17.2 

418 

22.4 

2600 

30710 

.422 

261 

9.80 

288:11.3 

313 

13.2 

340 

15.3 

366  17  .7 

416 

22.8 

2800 

33070 

.489 

267 

11.3 

290 

12.9 

314 

14.7 

338 

16.5 

363 

18.9 

411 

24.0 

3000 

35430 

.560 

273 

13.0 

294 

14.5 

317 

16.3 

340 

18.2 

362 

20.3 

409 

25.4 

3200 

37790 

.638 

279 

14.8 

300 

16.4 

320 

18.1 

341 

20.1 

363 

22.2 

406 

27.0 

3400 

40150 

.721 

288 

17.1 

307 

18.6 

327 

20.3 

344 

22.2 

364 

24.2 

405 

28.8 

3600 

42510 

.810 

294 

19.6 

314 

21.1 

332 

22.8 

350 

24.8 

369 

26.7 

407 

31.3 

3800 

44880 

.900 

339 

25.5 

356 

27.4 

372!  29.  5 

409 

33.9 

4000 

47240 

1.000 

362 

30.5 

378 

32.4 

411 

36.9 

APPENDIX 


323 


TABLE  XXIV. — No.  10  NIAGARA  CONOIDAL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 

total 
press. 

W  S.  P. 

H"  S.  P. 

H"  S.  P. 

«"S.P. 

W  s.  P. 

w  s.  P. 

a 
4 
« 

£ 

a 

d 

tf 

d 
H 

a 

d 
PJ 

d 

W 

a 

d 
tf 

d 

W 

a 

d 
PJ 

d 
W 

S 

d 

PS 

d 

a 

1000 

14580 

.063 

116 

.04 

145 

1.63 

1100 

16040 

.076 

115 

.16 

143 

1.74 

1200 

17500 

.090 

116 

.32 

143 

1.87 

167 

2.58 

1300 

18960 

.106 

118 

.50 

141 

2.04 

165 

2.73 

187 

3.52 

1400 

20410 

.122 

120 

.73 

142 

2.25 

164 

2.92 

185 

3.69 

206 

4.61 

1500 

21870 

.141 

123 

1.99 

143 

2.52 

163 

3.13 

184 

3.90 

204 

4.78 

223 

5.77 

1600 

23330 

.160 

126 

2.29 

144 

2.80 

164 

3.42 

183 

4.15 

202 

5.02 

220 

5.97 

1700 

24790 

.180 

129 

2.64 

147 

3.14 

165 

3.74 

182 

4.45 

201 

5.30 

218 

6.26 

1800 

26240 

.202 

133 

3.03 

150 

3.51 

166 

4.13 

183 

4.81 

200 

5.61 

217 

6.55 

1900 

27700 

.225 

137 

3.43 

153 

3.94 

168 

4.55 

184 

5.22 

200 

6.01 

216 

6.91 

2000 

29160 

.250 

141 

3.88 

156 

4.42 

171 

5.04 

185 

5.72 

200 

6.48 

216 

7.31 

2100 

30620 

.275 

145 

4.35 

159 

4.97 

174 

5.56 

187 

6.22 

201 

7.00 

216 

7.84 

2200 

32080 

.302 

149 

4.85 

163 

5.51 

177 

6.12 

190 

6.76 

203 

7.54 

217 

8.43 

2300 

33540 

.330 

154 

5.44 

1676.14 

1806.76 

193 

7.40 

205 

8.16 

218 

8.98 

2400 

34990 

.360 

158 

6.05 

171 

6.79 

183 

7.43 

195 

8.10 

207 

8.86 

220 

9.65 

2500 

36450 

.390 

163 

6.68 

175 

7.42 

187 

8.22 

198 

8.83 

210 

9.58 

222 

10.4 

2600 

37910 

.422 

168 

7.43 

179 

8.22 

190 

8.95 

202 

9.73 

213 

10.4 

224 

11.3 

2800 

40830 

.489 

177 

8.99 

187 

9.85 

198 

10.7 

208 

11.5 

219 

12.2 

230 

13.0 

3000 

43740 

.560 

187 

11.0 

197 

11.6 

206 

12.7 

216 

13.5 

226 

14.3 

234 

15.1 

3200 

46660 

.638 

215 

14.8 

224 

15.8 

234 

16.7 

243 

17.6 

3400 

49570 

.721 

242 

19.4 

250 

20.4 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

WS.P. 

iy2"  s.  P. 

WS.P. 

2"  S.  P. 

2M"  S.  P. 

a 

d 

ri 

d 
W 

a 

d 
tf 

d 

M 

a 

d 
P5 

d 
W 

a 

d 
PJ 

d 
W 

a 

3 

d 

W 

a 

d 

pj 

d 

B 

1300 

18960 

.106 

246 

6.40 

1400 

20410 

.122 

243 

6.59 

276 

8.83 

30811.1 

1500 

21870 

.141 

240 

6.83 

274 

9.00 

305 

11.5 

333 

13.9 

1600 

23330 

.160 

238 

7.05 

271 

9.34 

302 

11.8 

330 

14.3 

357 

17.0 

1700 

24790 

.180 

235 

7.28 

268)9.54 

299 

12.1 

326 

14.6 

353 

17.5 

403 

23.6 

1800 

26240 

.202 

233 

7.59 

265 

9.89 

295 

12.4 

323 

15.0 

350 

17.9 

399 

24.0 

1900 

27700 

.225 

232 

7.91 

263 

10.2 

293 

12.7 

320 

15.4 

347 

18.3 

395 

24.4 

2000 

29160 

.250 

231 

8.32 

262 

10.6 

291 

13.0 

317 

15.8 

343  18.7 

39l|24.9 

2100 

30620 

.275 

231 

8.77 

260 

11.0 

288 

13.5 

315 

16.2 

340 

19.2 

389 

25.4 

2200 

32080 

.302 

230 

9.31 

259 

11.4 

286 

13.9 

312 

16.6 

338 

19.6 

386 

25.9 

2300 

33540 

.330 

231 

9.92 

258 

12.0 

28514.4 

310 

17.1 

336 

20.1 

38126.4 

2400 

34990 

.360 

232 

10.6 

258 

12.5 

284 

15.0 

308 

17.7 

332 

20.6 

379 

27.0 

2500 

36450 

.390 

233 

11.4 

258 

13.3 

283 

15.6 

307 

18.2 

331 

21.2 

376 

27.6 

2600 

37910 

.422 

235 

12.1 

259 

14.0 

282 

16.3 

306 

18.9 

329 

21.8 

374 

28.2 

2800 

40830 

.489 

240 

13.9 

261 

15.9 

283 

18.1 

304 

20.4 

327 

23.3 

370 

29.6 

3000 

43740 

.560 

246 

16.0 

265 

17.9 

285 

20.1 

306 

22.4 

326 

25.0 

368 

31.3 

3200 

46660 

.638 

251 

18.3 

270 

20.3 

288!  22.  4 

307 

24.8 

327 

27.4 

365 

33.3 

3400 

49570 

.721 

259 

21.1 

276 

22.9 

294 

25.1 

310 

27.4 

328 

29.9 

364 

35.6 

3600 

52490 

.810 

265 

24.2 

283 

26.0 

299 

28.1 

315 

30.6 

332 

32.9 

366 

38.6 

3800 

55400 

.900 

305 

31.5 

320 

33.8 

335 

36.4 

368 

41.8 

4000 

58320 

1.000 

326 

37.6 

340 

40.0 

370 

45.6 

324 


HEATING  AND  VENTILATION 


TABLE  XXV. — No.  11  NIAGARA  CONOID AL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 

min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

K"S.P. 

W  S.  P. 

W  S.  P. 

M"S.P. 

w  s.  P. 

%"S.P. 

a 

a 
H 

s 

a 
ft 
8 

ft 

n 

a 

ft 
M 

ft 

H 

a 
A 
« 

a 
W 

8 
ft 
A 

S 

a 
0. 

H 

S 

1000 

17640 

.063 

106 

1.26 

132 

1.97 

1100 

19410 

.076 

105 

1.40 

130 

2.11 

1200 

21170 

.090 

106 

1.60 

130 

2.26 

152 

3.12 

1300 

22930 

.106 

107 

1.82 

128 

2.47 

150 

3.30 

170 

4.26 

1400 

24700 

.122 

109 

2.09 

129 

2.72 

149 

3.53 

168 

4.47 

187(5.58 

1500 

26460 

.141 

112 

2.41 

130 

3.05 

148 

3.79 

167 

4.72 

186 

5.78 

203 

6.98 

1600 

28230 

.160 

115 

2.77 

131 

3.39 

149 

4.14 

166 

5.02 

184 

6.08 

200 

7.22 

1700 

29990 

.180 

1173.20 

134 

3.80 

150 

4.53 

166 

5.39 

1836.41 

1987.68 

1800 

31750 

.202 

121 

3.67 

136 

4.25 

151 

5.00 

166 

5.82 

182 

6.79 

197 

7.93 

1900 

33520 

.225 

125 

4.15 

139 

4.77 

153 

5.51 

167 

6.32 

182 

7.27 

196 

8.36 

2000 

35280 

.250 

128 

4.70 

142 

5.35 

156 

6.10 

168 

6.92 

182 

7.84 

1968.85 

2100 

37050 

.275 

132 

5.26 

145 

6.01 

158 

6.73 

170 

7.53 

183 

8.87 

196 

9.49 

2200 

38810 

.302 

136 

5.87 

148 

6.67 

161 

7.41 

173 

8.18 

185 

9.12 

197 

10.2 

2300 

40580 

.330 

140 

6.58 

152 

7.43 

164 

8.18 

176 

8.95 

186 

9.87 

198 

10.9 

2400 

42340 

.360 

144 

7.32 

156 

8.22 

166 

8.99 

177 

9.80 

188 

10.7 

200 

11.7 

2500 

44100 

.390 

148 

8.08 

159 

8.98 

170 

9.95 

180 

10.7 

191 

11.6 

202 

12.6 

2600 

45870 

.422 

153 

8.99 

163 

9.95 

173 

10.8 

184 

11.8 

194 

12.6 

204 

13.7 

2800 

49400 

.489 

161 

10.9 

170 

11.9 

180 

13.0 

189 

13.9 

199 

14.8 

209 

15.7 

3000 

52910 

.560 

170 

13.3 

179 

14.0 

187 

15.4 

196 

16.3 

206 

17.3 

213 

18.3 

3200 

56450 

.638 

196 

17.9 

204 

19.1 

213 

20.2 

221 

21.3 

3400 

59980 

.721 

220 

23.5 

227 

24.7 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"  S.  P. 

1K"S.P. 

W  S.  P. 

W  S.  P. 

2"  S.  P. 

2K"  S.  P. 

a 
A 

rt 

ft 

W 

a 
A 
rt 

ft 
W 

a 
d 
« 

ft 
W 

a 
A 

H 

ft 

W 

a 
o< 
« 

S 

a 

ft 

« 

ft 

1300 

22930 

.106 

224 

7.74 

1400 

24700 

.122 

221 

7.97 

251 

10.7 

280 

13.4 

1500 

26460 

.141 

218 

8.26 

249 

10.9 

277 

13.9 

303 

16.8 

1600 

28230 

.160 

216 

8.53 

246 

11.3 

275 

14.3 

300 

17.3 

325 

20.6 

1700 

29990 

.180 

214 

8.81 

244 

11.6 

272 

14.7 

296 

17.7 

321 

21.2 

366 

28.6 

1800 

31750 

.202 

212 

9.18 

241 

12.0 

268 

15.0 

294 

18.2 

318 

21.7 

363 

29.0 

1900 

33520 

.225 

211 

9.57 

239 

12.4 

266 

15.4 

291 

18.6 

316 

22.2 

359 

29.5 

2000 

35280 

.250 

210 

10.1 

238 

12.8 

265 

15.7 

288 

19.1 

312 

22.6 

356 

30.1 

2100 

37050 

.275 

210 

10.6 

236 

13.3 

262 

16.3 

286 

19.6 

309 

23.2 

354 

30.7 

2200 

38810 

.302 

209 

11.3 

236 

13.8 

260 

16.8 

284 

20.1 

307 

23.7 

351 

31.3 

2300 

40580 

.330 

210 

12.0 

235 

14.5 

259  17.4 

282 

20.7 

306 

24.3 

346 

32.0 

2400 

42340 

.360 

211 

12.8 

235 

15.1 

258 

18.2 

280 

21.4 

302 

24.9 

345 

32.7 

2500 

44100 

.390 

212 

13.8 

235 

16.1 

257 

18.9 

279 

22.0 

301 

25.7 

342 

33.4 

2600 

45870 

.422 

214 

14.6 

236 

17.0 

256 

19.7 

278 

22.9 

299 

26.4 

340 

34.1 

2800 

49400 

.489 

218 

16.8 

237 

19.2 

257 

21.9 

276 

24.7 

297 

28.2 

336 

35.8 

3000 

52910 

.560 

224 

19.4 

241 

21.7 

259 

24.3 

278 

27.1 

296 

30.3 

335 

37.9 

3200 

56450 

.638 

228 

22.1 

246 

24.6 

262 

27.1 

279 

30.0 

297 

33.2 

332 

40.3 

3400 

59980 

.721 

236 

25.5 

251 

27.7 

267 

30.4 

282 

33.2 

248 

36.2 

331 

43.1 

3600 

63510 

.810 

241 

29.3 

257 

31.5 

272 

34.0 

286 

37.0 

302 

39.8 

333 

46.7 

3800 

67030 

.900 

277 

38.1 

291 

40.9 

305 

44.1 

335  50.6 

4000 

70560 

1.000 

296 

45.5 

309 

48.4 

336 

55.2 

APPENDIX 


325 


TABLE  XXVI. — No.  12  NIAGARA  CONOID AL  FAN  (TYPE  N)  CAPACITIES  AND 
STATIC  PRESSURES  AT  70°F.  AND  29.92  INCHES  BAROMETER 


Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  rain. 

Add 
for 
total 
press. 

K"  S.  P. 

w  s.  P. 

H"  S.  P. 

W  S.  P. 

H"S.P. 

K"  S.  P. 

a 
d 

pi 

d 

a 

a 

d 

pi 

d 
H 

a 
d 
« 

ft 

w 

a 
d 
rt 

ft 

a 

a 

d 
tf 

ft 

w 

a 
d 
rf 

ft 

a 

1000 

21000 

.063 

97 

1.50 

121 

2.35 

1100 

23090 

.076 

96 

1.67 

119 

2.51 

1200 

25190 

.090 

97 

1.90 

119 

2.69 

139 

3.72 

1300 

27290 

.106 

98 

2.16 

118 

2.94 

138 

3.93 

156 

5.07 

1400 

29390 

.122 

100 

2.49 

118 

3.24 

137 

4.21 

154 

5.31 

172 

6.64 

1500 

31490 

.141 

103 

2.87 

119 

3.63 

136 

4.51 

153 

5.62 

170 

6.88 

186 

8.31 

1600 

33600 

.160 

105 

3.30 

120 

4.03 

137 

4.93 

153 

5.98 

168 

7.23 

183 

8.60 

1700 

35690 

.180 

1083.80 

123J4.52 

1385.39 

152 

6.41 

168 

7.63 

1829.02 

1800 

37790 

.202 

111  4.36 

12515.06 

1385.95 

153 

6.93 

167 

8.08 

18119.43 

| 

1900 

39890 

.225 

114  4.94 

1285.67 

1406.55 

153 

7.52 

167 

8.66 

1809.95 

2000 

41990 

.250 

1185.59 

130  6.37 

14317.26 

154  8.24 

167 

9.33 

180  10.5 

2100 

44090 

.275 

121  6.27 

133 

7.16 

145 

8.01 

156 

8.96 

168 

10.1 

180 

11.3 

2200 

46190 

.302 

124 

6.99 

136 

7.94 

148 

8.81 

158 

9.74 

169 

10.9 

181 

12.2 

2300 

48290 

.330 

1287.83 

1398.84 

150!9.74 

161  10.7 

171 

11.8 

182 

12.9 

2400 

50390 

.360 

132 

8.71 

143 

9.78 

153 

10.7 

163 

11.7 

173 

12.8 

183 

13.9 

2500 

52490 

.390 

136 

9.62 

146 

10.7 

156 

11.8 

165 

12.7 

175 

13.8 

185 

15.0 

2600 

54590 

422 

140 

10.7 

149  11.8 

158:12.9 

168 

14.0 

178 

15.0 

187 

16.3 

2800 

58790 

.'489 

148 

13.0 

156 

14.2 

165 

15.4 

173 

16.6 

183 

17.6 

192 

18.7 

3000. 

62980 

.560 

156 

15.9 

164 

16.7 

172 

18.3 

180 

19.5 

188 

20.6 

195 

21.8 

3200 

67180 

.638 

179 

21.3 

187 

22.8 

195 

24.1 

203 

25.4 

3400 

71380 

.721 

202 

27.9 

208 

29.4 

Outlet 
velocity, 
ft.  per 
min. 

Capacity, 
cu.  ft. 
air 
per  min. 

Add 
for 
total 
press. 

1"S.  P. 

W'S.  P. 

1H"S.  P. 

1H"S.  P. 

2"  S.  P. 

2K"  S.  P. 

a 

d 
P3 

ft 

a 

a 

d 
tf 

ft 

a 

a 

d 

pi 

ft 

a 

a 

ft 

pi 

ft 

a 

a 
d 

« 

ft 

a 

a 

d 

« 

d 

a 

1300 

27290 

.106 

205 

9.22 

1400 

29390 

.122 

2039.49 

230 

12.7 

257jl6.0 

1500 

31490 

.141 

200 

9.84 

228 

13.0 

254 

16.6 

278 

20.0 

1600 

33600 

.160 

198 

10.2 

226 

13.5 

252 

17.0 

275 

20.6 

298 

24.5 

1700 

35690 

.180 

196 

10.5 

223 

13.7 

249 

17.4 

272 

21.0 

294 

25.2 

33634.0 

1800 

37790 

.202 

194 

10.9 

221 

14.3 

246 

17.9 

269 

21.6 

292 

25.8 

333 

34.6 

1900 

39890 

.225 

193 

11.4 

219 

14.7 

244 

18.3 

267 

22.2 

289 

26.4 

329 

35.1 

2000 

41990 

.250 

193 

12.0 

218 

15.3 

243 

18.7 

264 

22.8 

286 

26.9 

326J35.9 

2100 

44090 

.275 

193 

12.6 

217 

15.8 

240 

19.5 

263 

23.3 

283 

27.7 

324 

36.6 

2200 

46190 

.302 

192 

13.4 

216 

16.4 

238 

20.0 

260 

23.9 

282 

28.2 

322 

37.3 

2300 

48290 

.330 

193 

14.3 

215 

17.3 

238'20.7 

258 

24.6 

280 

29.0 

31838.0 

2400 

50390 

.360 

193 

15.3 

215 

18.0 

237 

21.6 

257 

25.5 

277 

29.7 

316 

38.9 

2500 

52490 

.390 

194 

16.4 

215 

19.2 

236 

22.5 

256 

26.2 

276 

30.5 

313 

39.8 

2600 

54590 

.422 

196 

17.4 

216 

20.2 

235 

23.5 

255 

27.2 

274 

31.4 

312 

40.6 

2800 

58790 

.489 

200 

20.0 

21822.9 

236 

26.1 

253 

29.4 

273 

33.6 

308 

42.6 

3000 

62980 

.560 

205 

23.0 

221 

25.8 

238 

29.0 

255 

32.3 

272 

36.0 

307 

45.1 

3200 

67180 

.638 

209 

26.4 

225 

29.2 

240|32.3 

256 

35.7 

273 

39.5 

304 

48.0 

3400 

71380 

.721 

216 

30.4 

230 

33.0 

245 

36.2 

258 

39.5 

273 

43.1 

303 

51.3 

3600 

75580 

.810 

221 

34.9 

236 

37.5 

249 

40.5 

263 

44.1 

277 

47.4 

305 

55.6 

3800 

79780 

.900 

254 

45.4 

267 

48.7 

279 

52.4 

307 

60.2 

4000 

83980 

1.000 

272 

54.2 

283 

57.6 

308 

65.7 

I 

INDEX 


Absolute  temperature,  4 

zero,  4 

Adiabatic  saturation,  199,  200 
Air  and  its  properties,  196-205 
Air,  composition  of,  196 

conditioning,  202,  203,  274-282 

cooling,  279-282 

distribution,  211,  218,  219 

-ducts,  239-252 

flow  of,  in  ducts,  239-252 

friction  of,  in  ducts,  239-252 

infiltration  of,  19,  20 

-line  system,  118;  119 

motion,  211,  212,  213 

pollution,  207,  208 

properties  of,  196-205 

psychrometric   chart  for,   201, 
202,  299-301 

specific  heat  of,  205 

supply,  208 

measurement  of,  209,  210 

tables,  203,  204 

total  heat  of,  199 

-valves,  137,  138 

venting,  149,  150 

-washers,  274-282 
Air-line  system,  118,  119 

valves,  138 
Anemometer,  243 
Anthracite  coal,  92,  93,  97 
Argon,  196 
Ash,  96 
Atmospheric  system,  119,  122,  123 

B 

Back  pressure  valve,  166 
Bacteria,  215,  218 


Bituminous  coal,  92,  93,  96 

Body,  heat  loss  from  the,  23 

Boilers,  92-112 

cast-iron,  98,  99 
connections  to,  156,  157 
downdraft,  101,  102 
firebox,  100 

magazine  feed,  103,  104 
marine  type,  100 
proportions  of,  104,  105 
rating  of,  105-108 
return  tubular,  99 
round,  98,  99 
sectional,  98,  99 
smokeless,  101-103 
steel,  99-101 
types  of,  98-101 
water  tube,  101 

Boot,  41,  42 

British  thermal  unit,  5 


Calorific  value  of  coal,  92,  94 
Carbon  dioxide,   95,   196,  197,   207, 
208,  218,  219 

monoxide,  95 
Carbonic     acid     gas.     See     Carbon 

dioxide. 

Centigrade  scale,  2 
Central  heating,  283-294 
Centrifugal  fan.     See  Fans. 
Check  valve,  132 
Chimneys,  110,  111 
Church  heating,  231-233 
Clinker,  96 

COa.     See  Carbon  dioxide. 
Coal,  92-94 

analysis  of,  93,  94 

composition  of,  93,  94 

consumption,  234,  235 

sizes  of,  93 


327 


328 


INDEX 


Coefficients  of  heat  transmission 
through  walls,  13-18,  295- 
298 

from  radiators,  77,  78 
Coke,  94,  95 
Cold-air  pipe,  39,  40 
Combustion,  95 
Comfort  chart,  216,  219 
Comfort  zone,  212,  213 
Conduction,  9,  10 
Conductivity,  10 

specific,  10 

Conduit,  for  pipes,  287-289 
Contractor's  guarantee,  81-83 
Convection,  9,  10,  74-76 

factor,  13,  14 
Cooling,  279-282 
Cost  of  heating,  234,  235 


I) 


Dalton's  law  of  gases,  198 
Damper,  227 

regulator,  109 
De-humidification,  281,  282 
Dewpoint,  198,  201 
Diaphragm  expansion  joint,  290 
Dirt  pocket,  153 
Disc  fan,  263 
District  heating,  293,  294 
Downdraft  furnace,  101,  102 
Draft,  110-112 
Drainage,  of  pipes,  146 
Drip  connections,  149,  150 
Dry  return  system,  116 
Dust,  215,  218 
Dynamic  head,  239 

E 

Economy  of  heating  systems,  32,  33 
Equivalent  evaporation,  105 
Estimating  of  heating  requirements, 

234,  235 
Expansion  fittings,  289,  290 

of  pipes,  145,  146,  148 

tank,  173,  174 
Exposure,  factors  for,  22 


Factory  heating,  230,  231 
Fahrenheit  scale,  2 
Fan  heaters,  263-271 

systems,  32,  224-273 
arrangement  of,  226 
design  of,  237-273 
types  of,  32 

Fans,  centrifugal,  blades  and  hous- 
ings, 254,  255 

disc,  263 

efficiency  of,  256 

laws  of, '256 

power  required  by,  255,  256 

straight  blade,  256,  257 

tables,  259-261,  302-325 

theory  of,  253,  254 
Fittings,  flanged,  130,  131 

screwed,  129,  130 
Flanges,  131 
Flow  of  air.     See  Air. 
Flues,  foul-air,  46 

Forced  circulation  hot-water  heat- 
ing, 184-188 
Friction,  of  air  in  pipes,  239-252 

of  fluids  in  pipes,  157,  158 
Fuels,  92-95,  96 

comparison  of,  96,  97 
Furnace,  boiler,  97,  101-103 

heating,  26,  34-48 

hot-air,  27,  35-38 

pipeless,  34 

G 

Gage,  109 

Gaskets,  131,  132 

Gate  valve,  132 

Generator,  183,  184 

Glass,  heat  transmission  of,  18 

Globe  valve,  132 

Grate  surface,  106,  107 

Grates,  25,  101 

Guarantee,  checking  of,  81-83 


Heat,  1-8 

definition  of,  1 


INDEX 


329 


Heat,  flow  of,  1 

given  off  by  persons,  23 
loss  of,  from  a  body,  9 
from  buildings,  9-24 
calculation  of,. 21,  22 
coefficients  of,  13-18,  295- 

298 

from  underground  pipes,   289 
measurement  of,  1,  4,  5 
of  superheat,  50 
of  the  liquid,  50,  51 
of  vaporization,  50,  51 
specific,  5,  6 
total,  52 
transmission  from  radiators,  67- 

78,  87,  88 
unit  of,  4,  5 

Heaters  for  fan  systems,  263-271 
friction  in,  268-270 
installation  of,  271 
pipe  coil,  264,  265 
vento,  263,  264,  265,  266-269 
hot-water,  112 
Heating,  cost  of,  234,  235 

different  methods  of,  25-33 

direct,  25,  28 

fan  systems  of,  30,  31 

furnace,  26 

hot  water,  28 

indirect,  25,  30 

of  auditoriums,  231-233 

of  factories,  230 

of  office  buildings,  225,  226 

of  schools,  226,  228,  229 

of  theatres,  231-233 

steam  required  for,  234,  235, 

236 

systems,  classification  of,  32 
economy  of,  32,  33 
hot-water,  28,  29,  168-188 
losses  in,  32,  33 
steam,  28,  113-126 
Horsepower,  boiler,  105 
Hot-air  furnace  heating,  27,  34-48 

pipes,  39-^6 

Hot-blaFt  system,  224,  225 
Hot-water  heaters,  112 

systems,  28,  168-188,  287 


Humidification,   39,   221,   276.     See 

also  Air  conditioning. 
Humidifier,  39,  221 
Humidifying  efficiency,  280 
Humidity,  absolute,  198,  199 
Humidity,  control  of,  278,  279 

measurement  of,  200,  201 

relative,  198,  199 

standards  of,  211,  212,  214 

See  also  Air  conditioning. 


Infiltration,  19,  20 
Intermittent  heating,  21,  22 


Joule's  equivalent,  8 

K 
k,  values  of,  18 

L 

Latent  heat,  50,  51 
Leaders,  40-44 

M 

Mercury  seal  generator,  183,  184 
Metering,  294 
Mixing  damper,  227 
Mixtures  of  substances,  54-58 
Moisture,  in  air.     See  Water  vapor 
and  Humidity. 

N 

Neon,  196 
Nitrogen,  196,  207 

O 

Odors,  214,  215,  218 
Office  buildings,  ventilation  of,  225, 
226 


330 


INDEX 


One-pipe  systems.     See  Single-pipe 

systems. 
Overhead  system,  steam,    117,  118, 

144 

water,  174,  175 
Oxygen,  196,  207 
Ozone,  196,  220 


Partial  pressures,  law  of,  198 
Petterson  and  Palmquist  apparatus, 

197 
Pipe,  127-129 

coil  heaters.     See  Heaters. 

coils,  156 

covering,  134-136 

dimensions  of,  128 

expansion  of,  145,  146 

fittings,  129-131 

flanges,  131 

hangers,  150,  151 
Pipe,  threads,  129 
Pipes,  hot-air,  39-46 

size  of,  for  steam,  159-164 
water,  177-183,  185-188 
Piping,  for  hot  water  systems,  183 

steam,  143-167 
Pitot  tube,  240,  241 
Plenum  chamber,  227 
Power  plants,  165,  166 
Pressure  drop  in  steam  pipes,  157- 
159 

gage,  109 

Proximate  analysis  of  coal,  93,  94 
Psychrometer,  201 
Psychrometric  chart,  201,  202,  299- 
301 

formula,    200 
Pumpage,  185 
Pumps,  circulating,  188 

vacuum,  125 
Pyrometer,  3 


R 


Radiation,  definition,  9 

transmission  of  heat  by,  9,  67-78 


Radiators,  61-91 
cast-iron,  61-64 
classification  of,  61 
connections  to,    154,  155,    163, 

164 

effect  of  enclosing,  71,  72 
of  length,  68,  69 
of  painting,  70 
of  shape,  68,  69 
of  width,  68,  69 
heat  transmission  from,  67-78, 

87,88 

heating  surface  of,  64 
indirect,  83-89 

location  of,  78-80  *  ,  ' 

pipe,  67 

pressed  metal,  65,  66,  78,  79 
semi-indirect,  89,  90 
tappings,  65 
wall  type,  64,  65 
Reducing  valve,  141 
Registers,  41,  42,  45 
Regulation  of  temperature,  189-195 
Relief  system,  115 
Retarder,  121 
Return  piping,  152,  164 
Risers,  149,  151 

hot-air,  40,  44,  45 


Safety  valve,  108,  109 
Saturation,  adiabatic,  200 
School  buildings,  226,  228,  229 
Separator,  140,  141 
Single-duct  system,  226,  228,  248- 
251 

-pipe  systems,  steam,  113-115, 

143 

water,  175 

Sling  psychrometer,  201 
Slip  joint,  290 
Smoke,  95,  96 

Smokeless  furnaces,  101-104 
Specific  heat,  definition,  4 

of  substances,  6 

of  water,  298 

of  air,  205 


INDEX 


331 


Split  system,  224 
Stacks,  110,  111 
Static  efficiency,  256 

head,  239 
Steam  boilers.     See  Boilers. 

consumption  of,  234-236 

flow  of,  in  pipes,  157-159 

formation  of,  49 

-heating  systems,  113-126 

piping,  143-167 

properties  of,  49-60 
table,  52,  53 

saturated,  49,  50 

superheated,  49 
Stefan's  law,  10 
Stoves,  26 
Synthetic  air  chart,  215-220 


Tapping  of  radiators,  65 
Temperature,  absolute,  4 
Temperature,  colors,  4 

control  of,  189-195 

definition  of,  1 

gradient,  14 

inside,  18,  19 

measurement  of,  2-4 

standards  of,  211,  212 
Theatres,  heating  of,  231-233 
Thermodynamics,  first  law  of,  8 
Thermometer,  2,  3 

wet-  and  dry-bulb,  199-201 
Thermostatic  control,  189-195 

of  fan  systems,  272 
Total  efficiency,  256 

heat,  52 
Traps,  bucket,  138;  139 

float,  138,  139 

radiator,  120,  121 

thermostatic,  120,  121 

tilting,  139,  140 
Trunk   duct  system,  225,  226,  251, 

252 

Tunnels,  291,  292 
Two-pipe  systems,  steam,   115-117 

water,  172-174 


U 


Underground  piping,  287-290 

Unions,  129,  130 

Unit  of  heat,  5 

Unit  ventilator,  233,  234 

Unwin's  coefficient,  157-159 


Vacuum  pump,  125 

system,  125,  126,  144,  152,  153 
Valves,  air-,  137,  138 

air-line,  138 

back-pressure,  166 

check,  132 

gate,  132 

globe,  132 

location  of,  153,  154 
Valves,  radiator,  122,  123,  133 

reducing,  141 
Vapor,  50 

system,   119-122,  123-125,  144, 
152,  153 

water.     See  Water  vapor. 
Vaporization,  heat  of,  50 
Velocity  head,  239 
Ventilation,  30-32,  206-223 

heat  required  for,  20,  21 

methods  of,  30,  31,  221,  222 

of  auditoriums,  231-233 

of  schools,  226,  228,  229 

of  theatres,  231-233 

requirements,  206,  207 

tests,   215-220.      See    also  Fan 

systems. 

Vento  heaters.     See  Heaters. 
Volatile  matter,  92,  94 

W 

Walls,    coefficients    of    heat    trans- 
mission through,  13-18 
flow  of  heat  through,  12-17 
Water  column,  108,  109 
pan,  39 

specific  heat  of,  298 
thermal  properties  of,  298 
vapor,  197,  198.     See  also  Hu- 
midity. 


332  INDEX 

Wet-    and    dry-bulb    thermometer,  Wolpert  method  of  CO2  determina- 
200,  201  tion,  197 

-bulb  temperature,  200  Wood  casing,  288 

-return  system,  116,  117 
Windows,    air  leakage  through,  20 

heat  loss  through,  18,  298  Zero,  absolute,  4 


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